The intrinsically sluggish kinetics of the oxygen evolution reaction (OER) remains a critical bottleneck for efficiently electrochemical water splitting, demanding catalysts that are both highly active and robust. Herein, this work overcomes this challenge through a heterostructure engineering strategy, fabricating a strongly coupled Ce(OH)3/NiFe2O4 heterogeneous interface on nickel foam (NF). This unique configuration is shown to critically modulate the catalyst's electronic structure and electrochemical reconstruction, unlocking substantial gains in OER performance. The optimized Ce(OH)3/NiFe2O4/NF catalyst exhibits exceptional OER performance, requiring a low overpotential of only 192 mV to achieve a current density of 10 mA‧cm−2 and a small Tafel slope of 40.7 mV‧dec−1, and demonstrating outstanding long-term stability for 400 h at 400 mA‧cm−2 in 1 M KOH. Mechanistic studies, including pH-dependent kinetics and molecular probe experiments, reveal that the OER process predominantly follows the lattice oxygen-mediated mechanism (LOM) of Ce(OH)3/NiFe2O4/NF, bypassing the scaling relations limitations of the conventional adsorbate evolution mechanism (AEM). Moreover, the in-situ Raman spectroscopy studies reveal a substantially decreased formation potential of the active NiOOH phase, while density functional theory (DFT) computations demonstrate that the interfacial coupling optimizes electronic structure via weakened metal-oxygen bonds and a modulated O-p band center in Ce(OH)3/NiFe2O4/NF. Besides, the integrated Pt/C||Ce(OH)3/NiFe2O4/NF electrolyzer exhibits excellent overall water splitting activity, demanding exceptionally low cell voltages of only 1.44 V and 1.58 V to achieve 10 and 100 mA‧cm−2, respectively. This work highlights the efficacy of rare-earth-based interface engineering in activating the LOM pathway and provides a valuable strategy for designing high-performance OER electrocatalysts.

Two-dimensional (2D) PdCu bimetallene (PdCu) exhibits unique structural and electronic properties, enhancing surface reactivity for crucial electrochemical reactions in energy conversion and storage. The one-pot synthesis, followed by dealloying (DA) to form DA PdCu, further enhances surface reactivity by altering the electronic structure. This process induces geometrical effects, significantly impacting surface strain and influencing selectivity and performance for (oxygen reduction reaction) ORR and (methanol oxidation reaction) MOR in an alkaline medium. The heterogeneous surface of DA PdCu with crystalline and amorphous regions and abundant surface defects, enhances active sites for improved ORR and MOR kinetics. During ORR, the DA PdCu exhibits superior mass activity (MA) of 0.62 mA μg−1 and extended stability with a positive shift (10 mV) in half-wave potential after 20,000 cycles. Additionally, it exhibits excellent MOR-MA (3335.9 mA mg−1) with 62.3% retention after 10,000 cycles, effectively competing with reported catalysts. Theoretical studies clarify the electronic strain transformation and its influence on adsorption energies of reaction intermediates on PdCu and DA PdCu during ORR and MOR, crucially correlating with experimental findings. The alloying-dealloying process in 2D-layered PdCu is a promising strategy to enhance the structure-activity relationship for improved multi-functional electrocatalysis with greater endurance.

This study presents a novel and straightforward approach to fabricate ultrafine, sharp-edged microneedle-like gold nanodendrites (Au NDs) on a homemade flexible screen-printed carbon electrode (FSPCE) using a one-step electrochemical deposition method. This aid to probe direct electrochemical oxidation and sensing of hydrazine. Effective monitoring of hydrazine is vital for risk reduction, safeguarding water quality, and ensuring safety in industrial and environmental application. The Au NDs@FSPCE offers a cutting-edge approach as an electrochemical sensor for hydrazine detection, facilitating the direct growth of Au NDs without reliance on binders or additional reductants. This advanced modification enhances the FSPCE with superior mechanical strength, excellent conductivity, tunable composition, and significantly improved electrochemical performance, establishing it as a highly efficient and reliable platform for hydrazine sensing. The Au NDs@FSPCE exhibited outstanding electrocatalytic performance at + 0.40 V with a higher oxidation current for hydrazine sensor. LSV studies revealed a detection limit of 0.46 µM, high sensitivities of 43.73 µAµM−1cm−2 and a rapid response time, and a broad linear range from 100 µM to 1500 µM. While chronoamperometry offered two linear ranges (10–90 µM and 190–1790 µM), with lower LOD of 10 nM. The sensor also demonstrated excellent long-term stability, strong reproducibility, and robust resistance to interference. Moreover, the Au NDs@FSPCE was successfully utilized to determine hydrazine in water samples.

Ternary nanostructured materials, fabricated by integrating three diverse metals, have been considered as promising cathode catalysts for fuel cells because of their synergetic effects and strain/ligand effects. That can result in effective charge transfer, weakened interactions with oxygenated species, and excellent methanol resistance. Owing to continued improvements in the production of ternary nanostructured materials, it is imperative to focus on recent advancements in this field. The present paper reviews different ternary nanostructures (i.e., support-free structures and supported catalysts), with an emphasis on their preparation methods, compositional and structural characteristics, as well as catalytic performance for oxygen reduction reactions (ORR). Moreover, the latest advances in ternary nanostructured catalysts for ORR at the cathodes of proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are highlighted. This work provides insights into designing advanced ternary catalysts with an analysis of challenging issues in developing highly efficient and stable nanomaterials for ORR electro-catalysis and suggests some perspectives for alleviating the difficulties toward practical implementation.

Highly sensitive ammonia (NH3) gas sensors play a critical role in various industries due to their direct implication for health and safety. Nanocomposites have gained massive attention for recent electrochemical gas sensing. In this work, we first propose a Ni-doped MnO2/Ti3C2Tx MXene nanocomposite material for electrochemical NH3 gas sensing at room temperature. Ni-doped MnO2 nanowires were introduced to Ti3C2Tx MXene using a self-assembly technique to develop a high-performance gas sensor. The nanocomposite was characterized using BET, SEM-EDS, XRD, and XPS analyses, which revealed that the Ni-MnO2 nanowires were uniformly distributed on the MXene surface, significantly increasing the surface area. The Ni-MnO2/Ti3C2Tx MXene nanocomposite was immobilized on a screen-printed carbon electrode (SPCE), which is the most appropriate platform for portable and convenient electrochemical sensors, and ionic liquid was used as an electrolyte to achieve high stability. Electrochemical analysis showed that this new NH3 gas sensor had outstanding performance with a higher sensitivity and a lower detection limit of 0.072 µA/ppm and 0.23 ppm, respectively. It also exhibited a fast response time of 45 s at 20 ppm NH3 gas, high repeatability, selectivity, and long-term stability. In addition, the electrochemical NH3 gas nanosensor was successfully demonstrated to monitor food freshness.

In this study, PtCo alloy nanoparticles (NPs) were successfully synthesized and deposited on nitrogen-rich carbon nanosheets derived from Polypyrrole-g-C3N4 using a chemical reduction method. This electrocatalyst not only offers enhanced catalytic efficiency but also significantly improves the stability for the oxygen reduction reaction (ORR) in in acidic medium. In terms of electrocatalytic performance, the PtCo/CN@PPY-g-C3N4 catalyst demonstrated a mass activity of 0.378 mA µgPt−1 at 0.85 V, 0.131 mA µgPt−1 at 0.9 V and a specific activity of 2.900 mA cmPt−2 at 0.85 V, 1.004 mA cmPt−2 at 0.9 V which are respectively 2.3, 2.8 and 10, 12 times higher than those of a commercial 20% Pt/C catalyst (0.166 mA µgPt−1 at 0.85 V, 0.046 mA µgPt−1 at 0.9 V and 0.285 mA cmPt−2 at 0.85 V, 0.079 mA cmPt−2 at 0.9 V). This indicates superior catalytic activity. Furthermore, after 5000 cycles, the PtCo/CN@PPY-g-C3N4 retained approximately 77% at 0.85 V and 83% at 0.9 V of its initial mass activity, with only a 14 mV decrease in the half-wave potential, whereas commercial 20% Pt/C catalyst retained only 40% at0.85 V and 30% at 0.9 V of its initial mass activity. These enhancements can be attributed to the synergistic effects and strong interactions between the Pt–Co alloy nanoparticles and the carbon nitride support. The findings of this study underscore the potential of PtCo/CN@PPY-g-C3N4 as a viable and efficient alternative to traditional catalysts in electrochemical applications.

Catalyst layer (CL) is the major component of proton exchange membrane fuel cells (PEMFCs) and routinely fabricated by a catalyst ink-based processing method. Such conventional CLs typically confront low activity, unaffordable Pt loading, and severe mass transport issues due to the thick and disordered structure, hampering the widespread commercial application of PEMFCs. Engineering of nanostructured CLs with low/ultralow Pt loading, ordered and/or ultrathin CLs, provides a highly promising pathway for overcoming these limitations. For the practical application of the nanostructured CLs in PEMFCs, this review comprehensively summarizes and comments on the important research and development of nanostructured CLs over recent years, involving ordered electronic conductor-based CLs, ordered ionomer-based CLs, and ultrathin CLs. The reviewed processes include (i) analyzing the motivation and necessity to design and fabricate nanostructured CLs based on the structure and mass transport process of conventional CLs, (ii) scrutinizing structure and composition, preparation methods, advantages, as well as some feasible strategies for the remaining challenges of various nanostructured CLs in detail, (iii) the progress of single cell activity and durability of the nanostructured CLs. Finally, some perspectives on remaining challenges and future development of the nanostructured CLs are presented to guide the exploitation for the next-generation of advanced CLs of PEMFCs.

Conversion of metal–organic frameworks (MOFs) into metal-nitrogen-doped carbon (M–N–C) catalysts requires a high-temperature process and longer processing time under a protective atmosphere. This study utilizes a low-energy nanosecond laser processing (LP) technique to convert aqueous synthesized 2D leaf-like Co-MOF (L-Co-MOF) into nanoscale cobalt metal encapsulated within a nitrogen-doped graphitic carbon matrix (Co@N-gC, Co-LP) in a shorter period under air atmosphere. The laser-induced process results in the formation of Co@N-gC with smaller Co particle size, uniform distribution, and better interaction with the carbon support compared to the conventional pyrolysis process (CP). LP catalysts result in enhanced multifunctional electrocatalytic activity over CP (Co-CP) catalysts owing to the tunable metal–support interaction, higher charge transfer, and presence of multiactive sites. Under optimized conditions (laser fluence: 5.76 mJ cm−2 and scan speed: 10 mm s−1), the Co-LP-5 catalyst exhibits better ORR performance, with onset and half-wave potentials of 0.92 and 0.76 V, respectively. Additionally, Co-LP-5 delivers excellent water-splitting performance, with OER and HER overpotentials of 380 and 280 mV, respectively, achieving an overall energy efficiency of 77.85%. Furthermore, Co-LP-5 demonstrates exceptional durability over 48 h of real-time testing, outperforming the Co-CP, and the proposed low-energy LP is viable for fabricating multifunctional catalysts.

The ability to synthesize multi-metal elements into a single-component material at the nanoscale, known as high entropy oxide (HEO) is earning great attention, especially in the field of electrocatalysis. However, the present methods for the synthesis of HEO often involve non-noble, noble, or refractory elements, which require complicated synthesis methods, making the control of shape and size highly challenging. In this regard, a class of six dissimilar elements (Co, Ni, Mn, Mo, V and Zn) with combination of non-noble and refractory elements has been formed a new type of (Co0.5Ni0.5Mn0.5Mo0.5V0.5Zn0.5)O based HEO. The multi-element interaction and carbonization network enhance ion conductivity, boosting specific capacitance to 698.4 F.g⁻¹, far surpassing conventional metal oxides. In addition, the HEO on screen printed electrode exhibited a notable increase in the oxidation peak current for the oxidation of dopamine, which can detect dopamine at nanomolar levels.

Toxic adverse effects to human beings caused by heavy metal ions resemble a serious threat to mankind and often appear in the journal headlines. However, simultaneous detection of heavy metal ions using analytical tools is challenging. In this regard, simultaneous electrochemical detection of Cd2+, Pb2+, and Hg2+ ions in water is presented using iron oxide (Fe2O3) nanostructures as spacers incorporated between microwave-exfoliated graphene oxide (MEGO). First, Fe2O3 nanostructures are synthesized using ferric nitrate in presence of poly(vinylpyrrolidone) and followed by their in-situ incorporation into expanded graphene oxide (GO). Exfoliated GO accommodates large amount of Fe2O3 nanoparticles via microwave-assisted method, minimizing the restacking of GO sheets. Consequently, Fe2O3-incorporated MEGO (Fe2O3-MEGO) fabricated on screen-printed electrodes (SPE) demonstrate well-separated anodic peak potentials at −0.65, −0.45, and +0.27 V for Cd2+, Pb2+, and Hg2+ ions. Moreover, Fe2O3-MEGO/SPE electrode exhibits wide linear range (0.4 to 74.78 μM), high sensitivities (8.11, 9.59, and 3.01 μA μM−1 cm−2) with low detection limits (0.2, 0.17, and 0.25 μM) for Cd2+, Pb2+, and Hg2+ ions, respectively. Therefore, this kind of incorporating nanomaterials as spacer molecules between GO allows for the design of alternative pathways to minimize restacking of GO and to increase sensitivity toward multiple targeted species.

Achieving efficient electrocatalysis for sustainably converting energy demands precise tuning of the structure-activity relationship of catalysts. Herein, we introduce a novel strategy for optimizing 2D PdCu bimetallene layers (BMLs) via an electrochemical dealloying (DA) process, modulating the electronic structures via lattice strain distortion. This boosts heterojunction surface activity and accelerates reaction kinetics, establishing DA PdCu BMLs as potential electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. At 10 mA cm−2, the DA PdCu BMLs achieve low overpotentials of 301 (OER) and 221 mV (HER) on a glassy carbon disc electrode. On carbon cloth electrodes in 1 M KOH, the DA PdCu BMLs achieve overpotentials of 177 (OER) and 127 mV (HER), outperforming the untreated PdCu BMLs that achieve 237 and 245 mV, respectively. Stability tests over 10,000 cycles reveal minimal degradation, with only a 3-mV shift in the OER overpotential, unlike the 22 and 54 mV for the PdCu BMLs and Pd/C, respectively. The PdCu and DA PdCu BMLs require 189 and only 161 mV to reach 10 mA cm−2 for the HER, respectively. Theoretical calculations show that electronic modulation alters OER and HER intermediate adsorption on PdCu and DA PdCu BMLs, which is in line with experimental observation. This study underscores the importance of electronic modulation and defect engineering in optimizing catalytic performance and stability for water splitting.

The escalating demand for sustainable hydrogen production has driven the exploration of biomass-derived carbon materials as cost-effective and eco-friendly alternatives to noble metal-based catalysts for water electrolysis. This review comprehensively examines recent advancements in synthesizing and optimizing biomass-derived carbon materials, including pyrolysis, hydrothermal carbonization, and microwave-assisted methods, alongside activation strategies such as physical, chemical, and templating techniques. These materials exhibit tunable porosity, heteroatom doping, and high surface area, enabling elevated catalytic performance toward both oxygen evolution (OER) and hydrogen evolution (HER) reactions. By integrating transition metals or heteroatoms (e.g., N, P, S), biomass-derived carbons achieve performance comparable to conventional Pt- or IrO2-based catalysts. Furthermore, bifunctional catalysts and hybrid electrolysis systems demonstrate synergistic efficiency, reducing overall energy consumption. Despite progress, challenges persist in pore structure regulation, conductivity enhancement, scalability, and long-term stability. This review underscores the potential of biomass-derived carbons to advance green hydrogen technologies while advocating for interdisciplinary efforts to address existing limitations and accelerate industrial adoption.

Intensified electrochemical corrosion under high-temperature and phosphoric acid conditions poses a significant challenge to the catalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, a S, P-doped hierarchical porous carbon nitride (S, P-HCN) supported PtCo alloy catalyst was developed to address this issue. The multilayered porous structure of S, P-HCN ensures high metal dispersion, a large specific surface area, and enhanced mass transfer. The PtCo/S, P-HCN catalyst exhibits remarkable performance, with specific activity (1.27 mA cmPt-2 at 0.80 V), mass activity (0.51 mA µgPt-1 at 0.80 V), and electrochemical active surface area (ECSA) (39.9 m2 g-1Pt), surpassing commercial 20 % Pt/C by 2–3 times. Durability tests over 5000 potential cycles reveal excellent retention of mass activity (84 %) and specific activity (83.2 %) at 0.80 V, with only a minor 14 mV shift in half-wave potential. This enhancement stems from the synergistic effects between PtCo alloy nanoparticles and S, P-HCN, which modulate Pt- electronic structure, strengthen metal-support interactions, and boost catalytic efficiency. Single-cell HT-PEMFC studies demonstrate a peak power density of 377.4 mW cm−2 for PtCo/S, P-HCN, comparable to commercial Pt/C (398 mW cm−2), with reduced voltage degradation at low current densities. This work presents a promising approach for improving cathode materials and advancing HT-PEMFC performance.

Integrating more active components into a catalyst material could facilitate the development of multifunctional electrocatalysts for energy conversion and storage applications. In this study, we developed a multifunctional electrocatalyst, namely, Pd alloyed with Co-Fe deposited on N-doped mesoporous carbon derived from tissue paper (Pd@Co-Fe/N-TDC). The synergism in Pd@Co-Fe/N-TDC, stemming from the interatomic alloy between Pd and Co-Fe, N-doped mesoporous carbon with defective surfaces, distribution of polyhedral Pd nanoparticles, and strong metal-support interfacial interaction, resulted in significantly high electrocatalytic performance for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Pd@Co-Fe/N-TDC was found to be an efficient bifunctional oxygen electrocatalyst, and this was evidenced by a high onset potential (1.01 V) and kinetic current density (2.6 mA/cm2) for the ORR and by a low overpotential (296 mV) and a low Tafel slope value (38 mV/dec) for the OER, along with a small ΔE of 736 mV. The catalyst also exhibited high durability for both ORR and OER, even after 10000 and 5000 cycles, respectively. Theoretical assessment provides an insight into the synergism of active metal sites in Pd@Co-Fe/N-TDC, which showed its potential for use as a non-Pt electrocatalyst for energy applications.

Platinum-group-metal-based polyhedral nanostructures generally possess high catalytic activity for electrochemical reactions owing to their numerous edges, corners, and well-defined lattice planes. However, their direct synthesis on common carbon powder is difficult, which considerably hinders their applications in practical devices. Herein, we report PtPd nanocubes (NCs) grown in situ on commercial carbon powder (Vulcan XC-72R) using a facile one-pot method. The as-prepared PtPd NCs/C (∼20 wt% metal) possess Pt-enriched surfaces, enabling the mass activity (MA) of methanol oxidation reaction (MOR) up to 1.77 A mgPt−1, which is 3.34/3.69 times that of commercial PtRu/C and Pt/C, respectively. With an average size of 8–10 nm, the PtPd NCs/C exhibit high stability, retaining over 80% initial MA against MOR in an accelerated durability test. For practical direct-methanol fuel cell (DMFC) operation, the PtPd NC/C as an anode catalyst delivered a maximum power density of 0.232 W cm−2 with high-concentration methanol (10 M) flow, which is 1.6 times higher than that for commercial PtRu/C under the same conditions. Moreover, the PtPd NCs/C demonstrated excellent durability for DMFC operation with much lower voltage decay than commercial PtRu/C, indicating its excellent potential for practical DMFC applications.

In pursuit of enhanced methanol tolerance and thermal stability, a cost-effective solution was developed by integrating varied proportions of zeolitic imidazolate framework-67 (ZIF-67), a metal-organic framework, into a sulfonated polyvinylidene fluoride (SPVDF) matrix-based proton exchange membrane (PEM). Through comprehensive characterization, the uniform dispersion and chemical functionalities of SPVDF and ZIF-67 was confirmed by Scanning electron microscopy(SEM), Fourier transform infrared spectroscopy (FT-IR) respectively. This uniform dispersion is attributed by the electrostatic interaction between the –NH2 group of Himm unit and -SO3H group of SPVDF create a strong hydrogen bonding network (i.e. acid-base pair) resulted in improved membrane surface hydrophilicity, water uptake, proton conductivity. Further the incorporation of ZIF-67 led to a composite membrane with significantly lower methanol permeability (1.5 × 10−7 cm2 s−1) compared to Nafion 117 (20 × 10−7 cm2 s−1). For glass transition and crystallization behavior of SPVDF-1 showed good miscibility enhance the membrane thermal and mechanical stability. This reduction is attributed to the presence of a large active surface area with small pores acting as a barrier against methanol permeation. Furthermore, single-cell tests in a direct methanol fuel cell (DMFC) demonstrated that the SPVDF-1 membrane achieves a maximum power density of 82.4 mW cm−2, surpassing that of Nafion 117 (75.9 mW cm−2). These results underscore the potential of the developed SPVDF-1 membrane as a promising alternative for DMFC applications.

In recent years, there has been notable progress in developing advanced catalyst materials and improving the performance of Pt-based catalysts for the oxygen reduction reaction (ORR). ORR is pivotal for achieving high energy conversion efficiency in fuel cells and metal-air batteries. Despite extensive research, balancing the activity and stability of electrocatalysts remains challenging. Due to the high cost and limited availability of Pt, there's a focus on developing Pt alloys, hybrid catalysts, and nanostructured materials with enhanced catalytic activity and utilization using cost-effective methods. Hybridizing multiple active components with Pt shows promise for achieving synergistic effects and meeting high-performance targets set by the U.S. Department of Energy for 2025. This review aims to present recent advances and assess the significance of supported and support-free Pt-based electrocatalysts for ORR. It focuses on carbon, inorganic, and hybrid support materials, as well as support-free metal nanostructures, highlighting their key features and catalytic potential. This offers valuable insights into developing novel Pt-based hybrid electrocatalysts for superior ORR performance in energy conversion and storage applications.

A hybrid catalyst support anchoring a noble metal catalyst could be a promising material for building interfacial bonding between metallic nanostructures and polymer functionalized carbon supports to improve the kinetics of oxygen reduction reaction (ORR). This study successfully prepared a polyhedron nanostructured Pd and MoO2-embedded polyaniline-functionalized graphitized carbon nitride (PANI-g-C3N4) surface using a chemical reduction method. The Pd–Mo/PANI-g-C3N4 achieved an ORR activity of 0.27 mA µg−1 and 1.14 mA cm−2 at 0.85 V, which were 4.5 times higher than those of commercial 20% Pt/C catalyst (0.06 mA µg−1 and 0.14 mA cm−2). In addition, the Pd–Mo/PANI-g-C3N4 retained ∼ 77.5% of its initial mass activity after 10,000 cycles, with only 30 mV half-wave potential reduction. Further, the engineered potential active sites in the catalyst material verified the significant improvement in the ORR activity of the catalyst with increased life-time, and theoretical calculations revealed that the synergistic effect of the catalytic components enhanced the ORR kinetics of the active sites.

A novel clay (aminoclay, AC) functionalized multi-walled carbon nanotube (MWCNT) was employed as a novel hybrid supporting material to Ag and Au nanoparticles for the improvement of oxygen reduction reaction (ORR). The size and structure of the catalysts were studied by XRD and electron microscopy analysis, revealing that the average crystallite and particle size was about 3.4 and 2.6 nm for Au and 16.2 and 15.3 nm for Ag nanoparticles, respectively. The ORR performance was probed by employing the voltammetry techniques under static and hydrodynamic conditions. The results show that the electrochemical surface area of Au (57.5 m2/g) and Ag (17.8 m2/g) on AC/MWCNT are larger than that of AC-free catalysts, and the ORR mechanism follows a direct 4-electron transfer pathway. The supported Au and Ag on AC/MWCNT catalysts explicitly showed the enhanced electrocatalytic efficiency and activity on ORR than that of the AC-free MWCNT catalysts. This work demonstrates that developing surface functionalized carbon support using an inorganic silicate layer (clay minerals) as hybrid support for the persistence of active metal catalysts could be a promising strategy for advanced LT-AFCs ORR electrocatalysts.

The catalyst layer (CL) is the only electrochemical reaction site in proton exchange membrane fuel cells (PEMFCs), decisive in their performance. Herein, a mild and simplified strategy is implemented into the in-situ growth of Pt–Pd alloy catalysts on the gas diffusion layer (GDL) as the CLs for PEMFCs. Pt/C is used as the nucleation site to assist the in-situ growth of the Pt–Pd CL. The as-prepared Pt–Pd CL behaves as a multi rhombic-pyramidal structure, which are evenly distributed on the GDL surface. The effect of the Pt/Pd atomic ratio on the electrocatalytic activity is investigated through a single-cell performance test, and the optimal atomic ratio is determined to be 1/2, which exhibits excellent cell performance and low activation polarization loss. Meanwhile, the single-cell test results reveal that Pt1Pd2 CL reaches optimal performance at a loading of 0.122 mg cm−2 (∼0.06 mgPt cm−2), with a peak Pt-specific power density of 14.23 W mg−1 (6.81 W mg−1 in PtPd), approximately 3.96 times that of a commercial Pt/C CL (0.2 mgPt cm−2). Furthermore, Pt1Pd2 CL shows significantly better stability than the commercial Pt/C CL, indicating that the in-situ preparation of the Pt-based CL has an excellent prospect for the commercial development of PEMFCs.

Mesoporous metallic nanomaterials possess high surface area and abundant three- dimensional channel structure for efficient transport of reactants, which are attractive for catalysis applications. In this work, we report a ternary PtPdCo mesoporous nanospheres (MNs), developed by a soft template-assisted method, as an efficient electrocatalyst for methanol oxidation reaction (MOR). The physicochemical characterizations demonstrate that PtPdCo MNs possess abundant mesoporous channels, nanospheres assembly of tiny nanoparticles, and strong interatomic interaction and synergistic effect. Electrochemical test shows that this unique metal alloy brings superior MOR catalytic performance. The mass activity (MA) and specific activity (SA) of PtPdCo MNs are 2.05 A mgPt−1 and 3.31 mA cm−2 respectively, which are 3.87/3.8 times of commercial PtRu/C, 4.27/4.47 times of commercial Pt/C. In addition, the measurements of i-t (3600 s) and ADT (2000 cycles) further revealed the superior durability of the PtPdCo MNs. These results indicate PtPdCo MNs outperform to reported benchmark catalysts and this study represents a novel approach to reducing Pt costs while achieving high MOR performance.

The effective regulation of catalytic active sites and reaction kinetics has been the key to promoting an efficient urea oxidation reaction (UOR). Herein, well-defined nickel-iron-vanadium layered double hydroxide nanosheets modified by sulfur incorporation (S-NiFeV LDH) on a nickel foam substrate are synthesized by a facile two-step hydrothermal method. Benefiting from the improved intrinsic activity and electrical conductivity derived from sulfur doping, and the large specific surface area of nanosheet architectures, the as-prepared S-NiFeV LDH catalyst shows a superior electrocatalytic performance with a low potential of 1.38 V at the current density of 100 mA cm−2 and the Tafel slope of 30.1 mV dec−1 in 1.0 M KOH and 0.33 M urea electrolyte. In addition, it displays robust stability while operating sustainably for 25 h at 50 mA cm−2 without any distinct activity attenuation. The results of density functional theory (DFT) calculations further indicate that the introduction of sulfur is more conducive to the adsorption of urea molecules on the catalyst surface, and the optimized Gibbs free energy of CO(NH2)2* decomposition and desorption of CO* and NH* in the S-NiFeV LDH catalyst facilitate accelerating the reaction kinetics of the UOR. Accordingly, this work provides a potential strategy for developing highly-efficient electrocatalysts for the UOR.

A simple and surfactant-free hydrothermal method was used to produce different forms of integrated nanostructures of Co3O4 spinel oxides, which exhibited excellent trifunctional electrocatalytic activity toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The surface morphology and structural features of Co3O4 spinel oxide catalysts were investigated, and 40–70-nm nanocube particles were found decorated over petal-, slab-, and flower-like spinel oxide structures with the dominant (111) crystalline plane. According to physicochemical studies, the Co3O4 spinel oxide catalyst with the slab morphology has a high Co3+/Co2+ ratio and an abundance of oxygen vacancies, resulting in improved trifunctional performance with an early ORR onset potential (0.91 V), low overpotential for OER (460 mV) and HER (363 mV), and extended durability. This study provides insights into the design and structural features of Co3O4 spinel oxides through a simple and template-free synthesis approach to compete as an efficient trifunctional electrocatalyst for water splitting and metal–air battery applications.

Engineering high-performance electrocatalysts to improve the kinetics of parallel electrochemical reactions in low-temperature fuel cells, water splitting, and metal-air battery applications is important and inevitable. In this study, by employing a chemical co-reduction method, we developed multifunctional Pt3Rh–Co3O4 alloy with uniformly distributed ultrafine nanoparticles (2–3 nm), supported on carbon. The presence of Co3O4 and the incorporation of Rh led to a strong electronic and ligand effect in the Pt lattice environment, which caused the d-band center of Pt to shift. This shift improved the electrocatalytic performance of Pt3Rh–Co3O4 alloy. When Pt3Rh–Co3O4/C was used to catalyze the oxygen reduction reaction (E1/2: 0.75 V), oxygen evolution reaction (η10: 290 mV), and hydrogen evolution reaction (η10: 55 mV), it showed greater endurance (mass activity loss of only 7%–17%) than Pt–Co3O4/C and Pt/C catalysts up to 5000 potential cycles in perchloric acid. Overall, the as-prepared Pt3Rh–Co3O4/C showed high multifunctional electrocatalytic potency, as demonstrated by typical electrochemical studies, and its physicochemical properties endorse their extended performance for a wide range of energy storage and conversion applications.

To date, the development of structure-sensitive electrocatalysts is crucial, consisting of oxophilic metals and a conductive support with Pt-rich surfaces. In this study, PtRh-Co3O4 ternary alloy nanoparticles (∼2–3 nm) were uniformly distributed on carbon (PtRh-Co3O4/C) via a co-chemical reduction method. The chemical inertness and oxophilicity of Rh, along with the abundant oxygen defects of Co3O4, contributed to improving the kinetics of the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) in PtRh-Co3O4/C by promoting the scission of C-C and C-H bonds. PtRh-Co3O4/C displayed high intrinsic activity for both MOR (6.8 mA/cm2Pt) and EOR (3.17 mA/cm2Pt) due to the strong electronic, ligand, and bifunctional effects. Even after 7000 potential cycles, it retained 81% (MOR) and 84% (EOR) of its initial value, indicating extended stability. Compared to other Pt-based benchmark catalysts, PtRh-Co3O4/C exhibited higher CO tolerance, extended activity, and stability, making it a promising electrocatalyst with competitive performance for alcohol electro-oxidation.

The direct methanol fuel cells (DMFCs) have motivated researchers to conduct multifaceted investigations by the virtues of inexpensive raw material and high energy density. Tuning the morphology and composition of Pt-based catalysts with one-dimensional (1D) nanostructures has been proved to be determinant to design high-performance electrocatalysts towards methanol oxidation reaction (MOR) for DMFCs. Over the past decade, significant progress has been achieved in improving the MOR activity of Pt-based catalysts. Herein, this review briefly presents several typical 1D Pt-based nanostructures, including nanowires, nanorods, nanochains, and nanotubes, for their applications in the MOR process. Some classic instances are listed and detailed to assist readers in better recognizing the superiorities of 1D Pt-based nanostructures. This review firstly focuses on the mechanism of action and evaluation parameters of Pt-based catalysts in MOR, then the strategies employed to synthesize 1D Pt-based nanostructures are briefly summarized. The importance of rationally designing 1D Pt-based catalysts for performance enhancement is emphasized by the MOR application of various 1D nanostructures. Finally, the conclusion and outlook for future research directions in this field were proposed to motivate future challenges.

This work shows that PANI-SnO2 nanorods with unique morphology and fine distribution of Pd-Ni alloy nanoparticles exhibit superior electrocatalytic performance toward methanol oxidation reaction (MOR). The amount of Ni content in Pdx-Niy/PANI-SnO2 nanorods plays a key role in Pd utilization. Ni in Pdx-Niy/PANI-SnO2 catalyst significantly reduces the CO adsorption on the active catalyst surface and enhances the electrode kinetics. The Pd3Ni1/PANI-SnO2 composite exhibits high mass activity (1861.9 mA mg−1) with extended stability even after 10000 cycles (∼90% retention) compared to other PdxNiy counterparts, Pd/PANI-SnO2, and commercial Pd/C catalysts. Interestingly, adding Ni along with SnO2 improves the electronic effect of Pd metal, significantly enhancing its catalyst activity and stability. Based on the results, we hope the present work brings an innovative approach to constructing efficient and cost-effective electrocatalysts for electrooxidation methanol in an alkaline medium.

The rational design of advanced transition-metal-based electrocatalysts with a heterostructure is a promising strategy for the promotion of the urea oxidation reaction (UOR) for energy-conservation technologies, but achieving a sufficiently high performance remains a challenge. In this work, we report a dramatic improvement in the UOR performance of a heterostructured electrocatalyst that combines NiMn-layered double hydroxide (LDH) nanosheets with NiCo2S4 arrays via a series of facile hydrothermal fabrication steps. Due to the high-flux electron transfer pathways at the close-contact interface, abundant active sites, and unique three-dimensional (3D) architecture, the NiCo2S4@NiMn LDH heterostructure grown on nickel foam exhibits a low potential of 1.37 V at a current density of 100 mA·cm-2 and a low Tafel slope of 43.8 mV·dec-1. More impressively, the proposed electrocatalyst demonstrates robust stability of more than 25 h at a current density of 50 mA·cm-2 with a negligible decrease in activity. In addition, density functional theory calculations reveal that the interface engineering within the heterostructure is beneficial for the adsorption and activation of urea molecules and the improvement of the sluggish UOR dynamics. The dissociation of adsorbed CO(NH2)2* into CO* and NH* intermediates on the heterostructured NiMn LDH is also facilitated by electronic coupling with NiCo2S4, resulting in superior UOR performance.

The authors regret an error in the published Fig. 5. In the revised Fig. 5. (below) panel (d) have been replaced with the chronoamperometry curves from the same sample. Therefore, the main conclusion of Fig. 5, viz. The stability comparison of Pdx-Niy/PANI-SnO2, Pd/PANI-SnO2, and Pd/C (Comm.) catalysts, are unaffected. The authors would like to apologise for any inconvenience caused. [Formula presented]

Nanoengineering effective bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains a major challenge in improving the performance of electrochemical energy conversion devices. In this study, we present a simple synthesis route for producing Co-Nx crystals that are effectively arranged on reduced graphene oxide layers (Co–N/RGO) through mechanochemical treatment. The Co–N/RGO catalyst performs well as a bifunctional oxygen electrocatalyst. Specifically, the Co–N/RGO-700 has an earlier ORR onset (0.91 V) and a half-wave potential (0.79 V) with a higher kinetic current density of 6.6 mA cm−2 than Pt/C, as well as a lower overpotential (430 mV) and Tafel slope (115 mV dec−1) for the OER. These results demonstrate outstanding performance compared to reported Co-based catalysts. Theoretical modeling and experimental results explore the Co–N/RGO active sites, as well as the vital role of electronic structure, abundant N content, and surface defects, confirming it as a potential electrode material for energy conversion applications.

Improved Bio-nanocomposite Materials for Emerging Energy Challenges. Nanocomposites derived from biorenewable sources have emerged as an important material for applications as diverse as energy storage, medicine, and environmental remediation. These nanocomposites have a high surface-to-volume ratio, facilitating easy fabrication, useful mechanical properties, and high thermal stability. As part of a two-volume set (1410 and 1411), this volume focuses on the principles, production, and applications of bio-nanocomposites, biomimetic nanocomposites, and additional nanostructured materials from biobased precursors. Chemists and engineers working in chemistry, materials science, nanotechnology, and chemical engineering will find these chapters useful.

Microalgal feedstocks have gained tremendous potential for sustainable biofuel production in recent years. For biofuel processing, thermochemical, biochemical, and transesterification processes are used. Many researchers have recently become interested in the hydrothermal liquefaction of microalgae. Renewable biofuel production from microalgae, as well as a broad range of value-added co-products, describe its potential as a biorefinery feedstock from this perspective. Microalgae convert solar energy into carbon storage compounds, such as TAG (triacylglycerols), which can then be converted into biodiesel, bioethanol, and bio-methanol. Microalgae are considered to be the most attractive source of biofuel production for all the organisms used. This review explored the percentage of oil content, chemical composition, and lipid content of microalgae. This analysis depicts the various aspects of microalgal species for biofuel conversion. Also, other bioenergy and value-added items are discussed briefly.

Oxygen reduction reaction (ORR) is a vital electrochemical reaction for energy conversion that has fascinated the interest of materials researchers to promote active and cost-effective electrocatalysts with improved reaction kinetics. Numerous, researches have been undertaken to achieve the desired characteristic cathode materials to revolutionize energy conversion devices including fuel cells and metal-air batteries (where ORR occurs). More importantly, the evaluation of electrocatalyst efficiency for ORR using typical electrochemical experiments, data collection, and analysis must be performed systematically and uniformly. This review provides a systematic guide to assess the electrochemical efficiency because it includes standard and widely recognized experimental protocols for each electrochemical technique, as well as easy-to-follow lab procedures and a detailed analysis of essential kinetic ORR parameters with a theoretical framework. The major function of each electrode in cyclic voltammetry, hydrodynamic linear scan voltammetry with rotating disc electrodes, and electrochemical impedance spectroscopy for ORR were demonstrated, as well as the construction of a three-electrode electrochemical cell. By following standard protocols and experimental procedures, an aspiring electrochemist would be capable to enforce fundamental and advanced electrochemical techniques much efficiently in their understanding of ORR kinetics evaluation.

Thermochemical conversion technologies have recently played a significant role in converting energy from waste sources. Thermochemical technologies have promisingways of recycling energy from variouswastematerials while reducing the environmental impact. This chapter primarily provides the collective information on waste feedstocks used for the thermochemical conversion from the recent review literature. Second, the numerous thermochemical conversion methods are discussed, including direct combustion, pyrolysis, gasification, and hydrothermal liquefaction using various reactors for each technique. It assesses the conversion of multiple wastes to crude bio-oil and the likelihood of converting syngas to biooil. Hydrothermal conversions occur at moderate temperatures, but typically at high pressure and in the presence of water. The thermochemical conversion includes the accurate temperature, pressure, and heating rate, which can be accomplished using various reactors. For the large-scale industrialization of biofuels, a greater understanding of the mechanism of conversion, reactors, and feedstock composition is crucial.Moreover, this chapter discusses the various thermochemical conversions of wastes and its bio-oil yield.

An efficient oxygen bifunctional catalyst Pt-Ru-Ir with ordered mesoporous nanostructures (OMNs) was successfully synthesized by chemical reduction using KIT-6 mesoporous silica as a template. The crystallographic behavior, electronic effects, and microstructure of the catalysts were investigated by XRD, XPS, SEM, and TEM analysis. The influence of OMNs and the effect of Ir content in Pt-Ru-Ir catalyst on both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated. The synergistic and electronic effects play an important role in electrocatalytic performance through the electronic coupling between Pt, Ru and Ir followed by the alloy formation with different lattice strain percentages. Amongst, the OMNs Pt70Ru25Ir5 catalyst exhibits the highest mass activity of 0.21 mA µg−1 and specific activity of 0.33 mA cm−2 for ORR, which are nearly 5-fold greater than those for benchmark Pt/C catalyst. Furthermore, the Pt70Ru25Ir5 demonstrated enhanced OER activity with an overpotential of 470 mV at 10 mA cm−2, an onset potential of 1.70 V, and a Tafel slope of 118 mV dec-1, outperforming commercial IrO2. In addition, the durability of the Pt70Ru25Ir5 catalyst for ORR and OER are found to be extended in comparison with that of other catalysts reported in this work after 6000 cycles. These results demonstrate that the ordered OMNs Pt-Ru-Ir with low Ir content (∼5 wt%) could be a promising oxygen bifunctional catalyst for electrochemical energy conversion and storage applications.

Engineering alloy nanostructures with a combination of highly active noble metals (Pt and Pd) and less electronegative non-noble metal (Ni) is found to be crucial for improving surface reactivity by enriching with active Pt sites. Herein, a multi-skeletal PtPdNi nanodendrites (NDs) was successfully formed by a simple one-pot method with structure directing agent. The modification of Pt electronic structure and their interaction due to compressive strain were explored using benchmark characterization techniques, which showed that the PtPdNi NDs possess Pt-enriched surface, corroborating to more active catalyst sites for oxygen reduction reaction (ORR) in acidic medium. The PtPdNi NDs have a higher electrochemical surface area (63 m2 g−1) and an earlier onset potential (1.01 V) than PtPd NDs, PtNi NDs, and commercial Pt/C catalysts, indicating the outstanding ORR performance. The high mass and specific activities, as well as superior durability after accelerated degradation test (ADT), highlight the remarkable electrocatalytic performance of PtPdNi NDs over others. As a result, enhancing Pt utilization through the formation of PtPdNi NDs could be a reliable strategy to improve ORR electrocatalysis for polymer electrolyte membrane fuel cell (PEMFC) applications.

Due to the bottlenecks in biofuel energy study, the production of an alternative and sustainable energy source with less environmental impact needs more focus. In general, renewable energy sources are environmentally friendly and could be a potential replacement for conventional energy sources such as fossil fuels and petroleum products. Biomass is considered a significant renewable and sustainable energy resource due to its large abundance and high energy efficiency. In bioenergy conversion technology, microalgae and macroalgae are still completely untapped with their feasibility as a sustainable green energy source. Hence, various energy conversion methods are used for biofuel production, playing an important role in bioenergy technology. Thermochemical conversion is considered a promising approach for bioenergy conversion of algal biomass. There are three thermochemical methods—pyrolysis (heating above 430°C), hydrothermal liquefaction (250°C-550°C), and gasification (above 700°C)—employed to produce biofuels. The thermochemical conversion technique is feasible and addressing the current difficulties of long-chain reaction time, poor conversion efficiency, and high-cost production will enable this technology to become commercially viable. This chapter aims to evaluate the various thermochemical conversions of species of algae. Furthermore, the different production yields of biooils and biooil consistency in other algae species were demonstrated.

Highly durable and active CeO2 on biochar carbon (CeO2/BC) derived from Spirulina platensis microalgae and synthesized by simple one-pot hydrothermal treatment and further activated through pyrolysis approach. A spindle-shaped morphology of CeO2 with predominant (111) facet was evidently observed from X-ray diffraction patterns and electron microscopy images. The structural features such as high specific surface area, defect-rich carbon with N & P atoms, increased oxygen vacancy and π-electron transfer play an important role for the improved oxygen reduction reaction (ORR). The considerable amount of Ce3+ and higher proportion of pyridinic N and graphitic N species are substantially contributed to the superior ORR performance of CeO2/BC700, which surpasses other similar catalysts and competing with Pt/C. Hence, the significant kinetic ORR parameters and extended stability (no loss after 5000 potential cycles) of the CeO2/BC700 catalysts provides the promising insight to develop the rare-earth metal oxide nanostructures as a possible candidate for ORR in alkaline medium.

The Pt-Fe2O3 nanoparticles embedded over N, P-doped carbon (Pt-Fe2O3/NPC) was successfully synthesized by chemical reduction method demonstrating an enhanced electrocatalytic efficacy in alkaline media toward oxygen reduction reaction (ORR). The surface morphology of Pt-Fe2O3/NPC has been characterized by electron microscopy scanning, X-ray diffraction, electron microscopy transmission, Raman spectra, and X-ray photoelectron spectroscopy. The ORR electrocatalytic activity of Pt-Fe2O3/NPC was found to be the superior mass activity of 0.120 mA µg−1, which are almost twice higher than those for Pt-Fe2O3/VC (0.068 mA µg−1) and Pt/C (0.061 mA µg−1) catalysts. The durability tests revealed that the Pt-Fe2O3/NPC exhibited enhanced stability observed from the order of electrochemical active surface area (ECA) loss determined as Pt-Fe2O3/NPC (45.67%) <Pt-Fe2O3/VC (62.5%) <(Pt/C (72.13%) after 5000 cycles. This present investigation unveiled a facile approach to develop the number of active sites with the combination between P-Fe2O3 and N, P-doped carbon for improved electrocatalytic performance toward ORR.

As a highly effective nanocomposite for hydrothermal liquefaction (HTL) of microalgae, the recycled biochar synthesized from Spirulina platensis and impregnated into CeO2 has been demonstrated. The order of in situ > ex situ > biochar nanocomposites for higher bio-oil. The highest bio-oil conversion of 33% was achieved at the optimum temperature of 250 °C. The use of the biochar nanocomposite also resulted in a decrease in the oxygen and nitrogen content of the bio-oil and an increase in its heating value, which was found to be high at 35.64 MJ/kg. With the inclusion of the in situ biochar nanocomposite, energy recovery was increased by up to 65.34%. The current study has shown that low biochar nanocomposite concentrations (0.20 g), low temperature (250 °C), and short residence time (30 min) are essential for improved bio-oil yield and quality of bio-oil.

Pt-based alloy nanomaterials with nanodendrites (NDs) structures are efficient electrocatalysts for methanol oxidation reaction (MOR), however their durability is greatly limited by the issue of transition metals dissolution. In this work, a facile trace Ir-doping strategy was proposed to fabricate Ir-PtZn and Ir-PtCu alloy NDs catalysts in aqueous medium, which significantly improved the electrocatalytic activity and durability for MOR. The as-prepared Ir-PtZn/Cu NDs catalysts showed distinct dendrites structures with the averaged diameter of 4.1 nm, and trace Ir doping subsequently improved the utilization of Pt atoms and promoted the oxidation efficiency of methanol. The electrochemical characterizations further demonstrated that the obtained Ir-PtZn/Cu NDs possessed enhanced mass activities of nearly 1.23 and 1.28-fold higher than those of undoped PtZn and PtCu, and approximately 2.35 and 2.67-fold higher than that of Pt/C in acid medium. More excitingly, after long-term durability test, the proposed Ir-PtZn and Ir-PtCu NDs still retained about 88.9% and 91.6% of its initial mass activities, which further highlights the key role of Ir-doping in determining catalyst performance. This work suggests that trace Ir-doping engineering could be a promising way to develop advanced electrocatalysts toward MOR for direct methanol fuel cell (DMFC) applications.

Mesoporous nanostructures of Pt alloy with Ru-Ir as trimetallic electrocatalyst exhibits significant performance for direct methanol fuel cell (DMFC). In this study, the ordered mesoporous nanostructure (OMNs) of Pt-Ru-Ir catalyst was prepared through the KIT-6 mesoporous silica template-assisted chemical reduction method. The OMN of Pt-Ru-Ir possesses high Pt utilization and a low Ir content, resulting in promoted MOR kinetics by the bi-functional mechanism of its oxophilic nature. In addition, the oxides of both Ru and Ir further enhanced the electrocatalytic efficiency of Pt by producing more active sites owing to its ordered mesoporous morphology and bifunctional mechanism. Furthermore, the OMNs of Pt0.7Ru0.25Ir0.05 electrocatalyst has a substantial electrochemical surface area (ECSA) of 78.35 m2 g−1 with 1721 mA mg−1 of mass activity, which is comparatively 2-3 times higher than all other catalysts reported here. Notably, the ECSA loss (19.5 %) after 5000 durability cycles was found much lesser than other compositions, Pt/C and Pt0.7Ru0.3 catalyst owing to the synergistic effect between Pt and Ru with a trace amount of Ir, smaller particle size, and unique ordered mesoporous morphology. Another significant factor is the rate of CO poisoning during MOR, which was found to be much lesser than others for the Pt0.7Ru0.25Ir0.05 catalyst (∼0.0047 %) studied by chronoamperometry test. The results indicate that the unique OMNs of Pt-Ru-Ir is an excellent MOR catalyst for DMFC applications.

The structure–activity-durability relationship of Pt nanoclusters anchored on aminoclay functionalized multi-walled carbon nanotube (Pt/AC-MWCNT) was well corroborated by the correlation between physicochemical properties and electrocatalytic oxygen-reduction (ORR) and methanol oxidation reactions. By TEM and XRD results, the closely-packed small Pt nanoparticles (~2 nm) forming an unique spherical-shaped nanocluster morphology with higher lattice strain (-0.432%) were determined. The dual functionality of Pt/AC-MWCNT has been substantially confirmed from the key electrochemical parameters of mass and specific activities for both ORR (0.223 mA μg−1 and 0.4 mA cm−2) and MOR (1688.8 mA mg−1 and 3.03 mA cm−2). After the accelerated durability test, the higher retention percentage of its initial catalytic activity for both ORR (5000 cycles) and MOR (2000 cycles) confirms the sustained stability of the catalyst. The superior performance of Pt/AC-MWCNT was attributed to, (i) the synergistic effect between Pt nanoclusters and hybrid support, (ii) the electronic effect by compressive lattice strain, and (iii) the shape of Pt nanocluster with tiny particles. Compared to commercial Pt/C (Alfa Aesar) and reported Pt-based nanostructures for ORR and MOR, the Pt/AC-MWNCT has shown promising dual-functional electrocatalytic efficiency.

In this work, the cerium oxide (CeO2) nanocatalyst was employed as a catalyst to enhance the hydrothermal liquefaction (HTL) of microalgae to bio-oil conversion. The HTL optimized parameters were obtained from response surface methodology (RSM). The Spirulina Platensis is blue-green algae were used to convert into bio-oil. The major processing method for bio-oil conversion was designed based on three key parameters, such as temperature, residence time and catalyst concentration. A remarkable enhancement of bio-oil production was observed for 0.20 g of CeO2 catalyzed HTL at 250 °C for 30 min, and around 26% of conversion was achieved which is higher than catalyst-free HTL reaction (16%). The synthetic CeO2 nanostructure was characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), brunauer-emmett-teller surface area (BET), X-ray powder diffraction (XRD) and thermal gravimetric analysis (TGA). The chemical composition of bio-oil was analyzed by gas chromatography-mass spectrometry (GC-MS) and the functional group analysis was done using fourier transform-infra red spectroscopy (FT-IR). The obtained results clearly reveal that the major chemical constituents such as hydrocarbons (7.55%), amino acids (36.69%) and nitrogen compounds (21.58%) for the bio-oil increased during CeO2 catalyzed HTL reaction. This investigation depicts that, the CeO2 nanoparticle could be employed as a potential candidate to accelerate the bio-oil conversion through HTL at low temperature from Spirulina platensis.

Platinum supported on carbon support (Pt/C) is currently the most common and practicable electrocatalyst for the real application of polymer electrolyte membrane fuel cells (PEMFCs). In this work, it was found that the nature of a reducing agent has noteworthy influence on Pt nanoparticles growth and distribution over acid-treated-Vulcan carbon support (Pt/AT-VC), which was employed to catalyze the oxygen reduction reaction (ORR) for PEMFC. Three distinct reducing agents, i.e., sodium borohydride (BH), sodium citrate (CA), and formaldehyde (FMY), were employed for Pt/AT-VC preparation through the impregnation-reduction approach. The impacts of the reducing agent on Pt nanoparticles size and its distribution over carbon support were scrutinized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) techniques. The electrocatalytic performance for ORR was subsequently studied by a three-electrode setup with rotating ring-disc electrode (RRDE) characterization and practical fuel cell operation. The ORR kinetics and mechanism were confirmed from RRDE, and it was well correlated with the durability test and single-cell results. Based on the results, the catalysts' performances for practical PEMFC can be arranged in the order of Pt/AT-VC (BH) < Pt/AT-VC (CA) < Pt/AT-VC (FMY), implying the significance of selecting the reducing agent for the preparation of Pt/C for PEMFC real application.

Pt-enriched surface layer formation on Vulcan carbon-supported Pd (Pt@Pd/C) was successfully prepared through a simple and one-pot formic acid reduction approach without any stabilizing agent. The electrocatalytic performance of Pt@Pd/C catalyst toward an oxygen reduction reaction (ORR) in alkaline medium was studied and also compared with standard carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts. The Pt@Pd/C exhibits higher electrochemical active surface area (74.7 m2/g) and mass activity (1.38 mA/μg) than Pt/C, Pd/C, and contending with standard reported catalysts. In durability tests, Pt@Pd/C showed negligible loss of intrinsic activity (∼10%) after 10,000 cycles which confirmed improved stability than Pt-based catalysts for ORR in KOH medium. This improved electrocatalytic performance could be attributed to their structural characteristics of the Pt-enriched surface layer on Pd/C-core and the compressive lattice strain on Pt. The present investigation demonstrates the simple preparation procedure for surface-enriched Pt on Pd/C and its improved performance for ORR, suggesting that it is a promising contender to benchmark ORR catalysts for alkaline fuel cells.

An effective bi-functional electrocatalyst of Co3O4/Polypyrrole/Carbon (Co3O4/Ppy/C) nanocomposite was prepared through a simple dry chemical method and used to catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Three types of carbon support as Vulcan carbon, reduced graphite oxide (RGO) and multi-walled carbon nanotubes (MCNTs) were used to study the influence on electrochemical reactions. Spherical shaped Co3O4 nanoparticles with 8–10 nm was found uniformly distributed on Ppy/C composite, which were analyzed by X-ray diffraction and transmission electron microscopy techniques. Amongst, Co3O4/Ppy/MWCNT shows improved bifunctional electrocatalytic activity towards both OER and HER with relatively low over potential (340 mV vs. 490 mV at 10 mA cm−2) and Tafel slope (87 vs. 110 mV dec−1). In addition to that, MWCNT supported Co3O4/Ppy nanocomposite exhibits good electronic conductivity and electrochemical stability up to 2000 potential cycles. The results clearly indicate that the Co3O4/Ppy/MWCNT nanocomposite could be the promising bi-functional electrocatalyst for efficient water electrolysis.

Development of highly active and durable Pt based anode materials with higher utilization of Pt is quite crucial towards the commercial viability of direct methanol fuel cells (DMFCs). Herein, multi-walled carbon nanotube supported PtxIr nanostructures (PtxIr/MWCNT) are successfully prepared by one-pot wet chemical reduction without any surfactants. The role of Ir content and its bi-functional mechanism on kinetics of methanol oxidation reaction (MOR) was studied. The MOR on PtxIr/MWCNT follows Langmuir-Hinshelwood mechanism by successive oxidative removal of CO. The co-existence of IrO2 plays a vital role as catalytic promotor. Amongst, Pt2Ir/MWCNT shows enhanced electrocatalytic activity (mass activity (MA), 933.3 mA/mgPt) and durability (13.8% loss of MA after 5000 potential cycles) thru the well-balanced electronic and bi-functional effects. This study implies that the optimized composition of Pt2Ir/MWCNT exhibits efficient methanol oxidation and could be a potential catalyst for direct methanol fuel cells.

In this study, a simple and environmentally amicable synthesis procedure for support-free silver-rhodium (Ag-Rh) bimetallic network-like nanoalloy was used to catalyze an oxygen reduction reaction in an alkaline medium. The support-free network-like morphology of Ag-Rh nanoalloy exhibits a higher electrochemical surface area (ECSA) of 65.6 m2/g than carbon (VC) supported Ag-Rh (23.8 m2/g). In comparison to the reported benchmark Ag-based electrocatalysts, it presents an improved mass and specific activity of 971.1 mA/mg and 1.45 mA/cm2, respectively. Based on the durability test, the support-free Ag-Rh catalyst retains ∼70% of its initial ECSA after 7000 potential cycles, and Ag-Rh/VC possesses only 20% after 5000 potential cycles due to the surface oxidation of carbon support. Hence, the superior electrocatalytic performance attributed to the support-free morphology and alloy formation with Rh was clearly demonstrated, which could potentially be the choice of the cathodic electrocatalyst for alkaline fuel cells.

In this work, a facile Fe- and N-containing porous carbon derived from sewage sludge was prepared and served as the support of Pt nanoparticles for the electrooxidation of methanol. Both the sludge-derived carbon (denoted as SC) and the resultant Pt/SC catalyst was physically characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The electrocatalytic performance for methanol oxidation reaction (MOR) of the Pt/SC was examined by cyclic voltammetry (CV) and chronoamperometric method. The results showed that the Pt/SC possessed slightly larger Pt particle size (5.5 nm) and lower electrochemical active surface area (ECA) compared to common Pt/C catalyst. However, the mass activity of Pt/SC for MOR was up to 201 mA mg−1, which was much higher than that of Pt/C (93 mA mg−1), indicating the synergistic effect of the sewage sludge-derived carbon with Fe and N species on methanol electrooxidation. Furthermore, Pt/SC showed enhanced durability towards MOR compared to common Pt/C, implying its potential for using in direct methanol fuel cell (DMFC) for energy conversion, which also demonstrated a promising solution for the utilization of sewage sludge resources.

The mesoporous carbon layers protected Fe-N nanocrystals (Fe-N-Csyn) was successfully synthesized by a simple hydrothermal approach and displays an improved oxygen bi-functional performance. The high specific surface area, mesoporous and graphitic carbon with more active sites of Fe-Nx and Fe3C/Fe in Fe-N-Csyn favors good synergistic electrocatalytic effect toward oxygen reduction and oxygen evolution reactions (ORR and OER) in alkaline medium. The bi-functional activity of Fe-N-Csyn was clearly observed from the earlier onset potential of 0.86 V and limiting current density of 5.23 mA cm−2 for ORR, as well as the low over potential of 470 mV with small Tafel slope value of 84 mV dec−1 for OER. The enhanced stability and improved oxygen bifunctional activity of Fe-N-Csyn catalyst was evidently demonstrated through an innovative synthesis approach for the development of earth-abundant metal catalysts for energy applications.

In this work, the trimetallic PtPdCr nanoparticles with low platinum loading (~5 wt%) supported on Vulcan carbon (PtPdCr/C) were synthesized through a facile two-step co-reduction method and showed superior methanol oxidation activity. The particle size distribution, morphology and elemental composition of the PtPdCr/C were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The electrochemical performance for methanol oxidation of the PtPdCr/C was found to be higher with the mass activity of 969 mA·mg−1Pt compared to Pt/C (581 mA·mg−1Pt) and PtRu/C (725 mA·mg−1Pt). Moreover, the stability studies confirmed the enhanced durability of PtPdCr/C over Pt/C and PtRu/C catalysts after the accelerated durability test (ADT) and chronoamperometry (CA) analysis. The increased methanol oxidation activity and durability of the trimetallic PtPdCr/C in acid medium can be attributed to the change in binding energy of Pt and the induced synergistic effect from Pd and Cr atoms to Pt, which demonstrated a promising strategy for the preparation and utilization of ternary alloy catalysts towards methanol electrooxidation.

Pt-based catalysts are still most attractive and could be the major driving force for facile electrochemical reactions in direct methanol fuel cells (DMFCs). In this work, a Pt3Mn nanowire network structures (NWNs) catalyst was successfully synthesized by a soft template (CTAB) method. The morphology and elemental composition of the Pt3Mn NWNs were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The electrocatalytic behavior of the synthesized Pt3Mn NWNs catalyst towards methanol oxidation reaction (MOR) was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The results reveal that the Pt3Mn NWNs has superior MOR activity and durability compared to Pt NWNs and commercial Pt/C. The mass and specific activities of Pt3Mn NWNs are 0.843 A mg−1 and 1.8 mA cm−2 respectively, which are twice that of commercial Pt/C. Additionally, the results of CA test indicate that the Pt3Mn NWNs possesses better durability than Pt NWNs and commercial Pt/C catalysts in acidic media, which is expected to be a new alternative anode material in DMFCs.

Multi-walled carbon nanotube supported Pt–Ir nanoparticles (Pt–Ir/MWCNT) with different elemental ratios were synthesized by one-pot co-reduction approach under ambient conditions. The Pt–Ir catalysts exhibit improved bi-functional activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and its electrocatalytic performance was clearly established using different physiochemical characterization techniques. The Pt–Ir composition of 2:1 has a higher electrochemical surface area (ECSA) of about 85.3 m2/g compared to other compositions (3:1 and 1:1) and Pt/MWCNT due to the effect of particle size distribution. The improved ORR/OER activity was found to be 139.4 and 740 mA/mg, respectively, for Pt–Ir(2:1)/MWCNT with the potential difference of 760 mV for oxygen bi-functional activity. Furthermore, Pt–Ir(2:1)/MWCNT showed much better stability for ORR compared to other compositions and Pt/MWNCT catalysts, i.e., around 76% of its initial ECSA retained with <20 mV shift in half-wave potential was obtained even after 10,000 potential cycles in acidic medium. It is believed that the Pt enriched surface, amount of Ir content, induced electronic and geometric effects play a vital role on the electrocatalytic activity enhancement of Pt–Ir(2:1)/MWNCT as effective bi-functional oxygen electrode.

The aim of the present work was focused on optimizing the hydrothermal liquefaction (HTL) of Spirulina platensis catalyzed by Fe3O4 nanostructures to enhance the bio-oil yield and quality of bio-oil using response surface methodology (RSM). The structural morphology and crystalline nature of the synthesized catalyst was determined using a scanning electron microscope (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray powder diffraction (XRD). Three of the vital reaction parameters such as temperature, holding time and catalyst dosage were optimized through central composite design. A maximum bio-oil yield of 32.33% was observed for the high temperature at 320 °C, 0.75 g of catalyst dosage and 37 min of resident time. The maximum conversion was found at a lower temperature of 272 °C, the bio-oil yield of 27.66% was obtained with 0.45 g of catalyst dosage and 24 min of holding time which is an energy efficient optimum condition. The maximum bio-oil yield was influenced at a lower temperature due to the high catalytic activity. While compared to higher temperatures were not much influence was observed. It clearly states that the catalyst dosage playing a critical role in the lower temperature HTL reaction. GC-MS and FT-IR analysis of the produced bio-oil exhibits significant characteristics for biofuel applications. The Fe3O4 catalyst was recyclable for up to eight repeated cycles and constant bio-oil yield for the last four cycles. It shows the excellent reproduction ability towards HTL of Spirulina sp.

Self-supported silver nanoflowers (AgNFs) and unmodified multi-walled carbon nanotube (MWCNT) supported silver nanostructures (Ag/MWCNT) were synthesized by an environmentally amicable slow chemical reduction method using ascorbic acid at room temperature. Structural morphologies were analyzed by scanning and transmission electron microscopic techniques and crystallinities were determined by X-ray diffraction method. Electrocatalytic activities for oxygen reduction reaction (ORR) were investigated for both Ag NF and Ag/MWCNT catalysts using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). From CV profiles the electrochemically active surface areas of Ag NF and Ag/MWCNT were estimated to be 87.7 m2/g and 19.8 m2/g respectively. The LSV showed the maximum limiting current densities of 4.7 and 3.76 mA/cm2 at the electrode rotation rate of 2400 rpm with specific activities of 1.26 and 1.06 mA/cm2 measured at −0.1 V for Ag NF and Ag/MWCNT, respectively, confirmed their high ORR activities in 0.5 M KOH medium. Accelerated durability tests revealed that Ag/MWCNT possessed an excellent stability, that is, it has retained nearly 83% of its initial activity after 3000 potential cycles, which is much higher than modified MWCNT supported Ag catalyst reported in literature.

Pt3M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple chemical reduction approach, and employed as the promising electrocatalyst to accelerate the kinetics of oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells. From XRD, the positive shift of diffraction angle confirms the alloy formation between Pt and M and the elemental composition was confirmed by energy dispersive X-ray spectroscopy analysis. The nanocluster morphology and particle size was determined using scanning and transmission electron microscopy analysis. The ORR kinetic parameters for Pt-M electrocatalysts were calculated and compared with reported Pt/C catalysts. Among the Pt-M electrocatalysts, Pt-Co was found to be the most efficient catalyst having the higher mass and specific activity (at 0.9 V vs. RHE) of 0.44 mA/μg and 0.69 mA/cm2, respectively. The accelerated durability test reveals that the Pt-M bimetallic alloy nanoclusters retain appreciable surface area and mass activity after 8000 potential cycles confirms good long-term durability, and also competing with the reported benchmark ORR catalysts. [Figure not available: see fulltext.]

The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh NSs) synthesized by a surfactant template-free, single step chemical reduction method occurred with high intrinsic activity in an alkaline medium. Cyclic voltammetry and linear scan voltammetry together with X-ray diffraction and high-resolution electron microscopy showed that the improved performance of the Au-Rh NSs toward dioxygen reduction could be due to the synergistic electronic effects of nanobimetallic combination and its clusterlike morphology. The electrochemically active surface area (ECSA) was estimated to be 37.2 m2 g-1 for supportless Au-Rh NS with a 3:1 atomic composition, which was higher than that reported for Ag-based nanocatalysts. The intrinsic activities (IA) of the supportless and carbon supported Au-Rh (3:1) NSs were 3.25 and 3.0 mA/cm2, respectively, which were higher than those of the standard Pt/C (0.1 mA/cm2)45 Au/C catalysts for the oxygen reduction reaction (ORR). Oxygen reduction on both catalysts followed a direct four electron pathway. The accelerated durability test carried out by continuous potential cycling showed that the 3:1 ratio of Au-Rh nanostructures had excellent stability with a 20% increase in ECSA after 10 000 potential cycles, highlighting their potential application for real systems.

The amino functionalized magnesium phyllosilicate clay (AC) intercalated over PVA-Nafion hybrid nanocomposite membranes were prepared by sol-gel method. The free standing membranes were obtained by solution recasting. The composition of clay materialssuch as AC and montmorillonite (MMT) was varied between 2-10 wt.% with respect to PVA-Nafion content. The molecular interactions and surface morphology of nanocomposite membranes wereinvestigated by FT-IR and SEM analyses respectively. The thermal and mechanical stabilities of nanocomposite membranes were studied using TGA and Nanoindentation techniques. For 6 wt. % AC/PVA-Nafion, TGA results showed no appreciable mass change up to 380 °C and hardness calculated from nanoindentation studies was nearly 30 % higher than the other compositions. An improved conductivity was obtained for 6 wt. % AC/PVA-Nafion (1.4×10-2 S/cm) compared to pure Nafion (1.2×10-2 S/cm) and PVA-Nafion and MMT/PVA-Nafion composite membranes. From these studies, we observed that 6 wt. % AC/PVA-Nafion membrane possessed a good conductivity with higher thermal and mechanical stabilities.

A novel aminopropyl functional group bearing magnesium phyllosilicate clay (AC)/Nafion nanocomposite films with embedded platinum nanoparticles (Pt/AC/N) was prepared by sol-gel method followed by solution casting for various compositions of AC in Nafion. The as prepared nanocomposite films were subjected to surface characterization by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The thermal and mechanical stabilities were analyzed by thermogravimetric analysis (TGA) and nanoindentation coupled scanning probe microscopy analysis (SPM). The protonic conductivity of AC/Nafion nanocomposite films with and without Pt nanoparticles was measured by electrochemical impedance spectroscopy (EIS) using a two-probe conductivity cell. It was found that 6wt.% AC/Nafion possesses a high proton conductivity of 1.38×10-4Scm-1, a thermal stability of up to 360°C (60°C higher than pristine Nafion) and a high mechanical stability (78.76MPa) among the different compositions studied. The catalytic activity of the optimized nanocomposite film containing Pt nanoparticles (Pt/6wt.% AC/N) towards oxygen reduction reaction (ORR) was investigated by cyclic voltammetry (CV) and linear scan voltammetry (LSV) techniques under hydrodynamic conditions. It was observed that 35.4μgcm-2 Pt/6wt.% AC/N composite film has higher ORR limiting current density of 4.2mAcm-2, and also it is interesting to note that this composition exhibited a high conductivity of 1.75×10-3Scm-1 indicating that the nanocomposite catalyst film could be used as a proton conductor as well as a catalyst layer for the fabrication of membrane electrode assemblies in PEM fuel cells.

The reduction reaction of molecular oxygen (ORR) was investigated using supportless Pt nanonetwork (Pt NN) electrocatalyst in sulfuric acid medium. Pt NN was prepared by template free borohydride reduction. The transmission electron microscope images revealed a network like nano-architecture having an average cluster size of 30 nm. The electrochemical characterization of supportless and Vulcan carbon supported Pt NN (Pt NN/VC) was carried out using rotating disc and ring disc electrodes at various temperatures. Kinetic and thermodynamic parameters were estimated under hydrodynamic conditions and compared with Pt NN/VC and reported Pt/C catalysts. The accelerated durability test revealed that supportless Pt NN is quite stable for 5000 potential cycles with 22% reduction in electrochemical surface area (ECSA). While the initial limiting current density has in fact increased by 11.6%, whereas Pt NN/VC suffered nearly 55% loss in ECSA and 13% loss in limiting current density confirming an enhanced stability of supportless Pt NN morphology for ORR compared to conventional Pt/C ORR catalysts in acid medium. © 2014 Elsevier Ltd.

Self-stabilized Pt-Rh nanoclusters (NCs) were prepared by using a surfactant-free chemical reduction method with formic acid as the reducing agent. The elemental composition was determined by EDX analysis. The synthesized cluster was used as a supportless (SL) electrocatalyst for the reduction of oxygen (ORR) in acid medium. The composition of Pt-Rh bimetal NCs, in terms of atomic weight percentage, was optimized based on the available electrochemical surface area. Hydrodynamic linear scan voltammetric profiles show that the onset potential for oxygen reduction is 0.78 V vs. RHE at the electrode rotation rate of 2400 rpm with 17.8 μg cm-2 loading of the SL Pt3Rh exhibiting the limiting current density of 3.5 mA cm-2. The durability of the electrocatalysts was investigated by performing the accelerated durability test (ADT): the electrochemical surface area (ECSA) for SL Pt3Rh increased by nearly 9.2% while retaining nearly 85% of its initial limiting current density after 15000 potential cycles. For comparison Vulcan-carbon-supported Pt3Rh was synthesized under identical conditions and subjected to electrochemical investigations. Both supportless and VC-supported Pt3Rh NC electrocatalysts were found to use a direct 4-electron transfer mechanism. In order to improve the activity, SL Pt@Pt3Rh NC was synthesized and used as the catalyst. At 0.9 V, the mass activity (0.085 mA μg-1) of the Pt@Pt3Rh NC was found to be nearly 34 times greater than that of SL Pt3Rh NC (0.0025 mA μg-1). We conclude that the SL Pt3Rh NC could potentially be used as an electrocatalyst for ORR in a sulfuric acid medium since it possesses good stability compared to Pt-based ORR catalysts reported in the literature.

Synthesis and electrochemical characterization of carbon supported platinum nanoparticles dispersed over Nafion-Polyethylene glycol bipolymeric nanocomposite film (Pt/VC/NP) was attempted for catalyzing the oxygen reduction reaction (ORR) in sulfuric acid medium. The nanocomposite films were surface characterized using Scanning electron microscope, X- ray diffraction pattern, X-ray fluorescence spectroscopy and Atomic force microscopy analyses. The electrochemical behavior was studied using cyclic voltammetry and linear scan voltammetry under static and hydrodynamic conditions to check the catalytic ability of the electrocatalyst films towards ORR. A good correlation was seen between the conductivity of the nanocomposite films from electrochemical impedance spectroscopy and the ORR activity. The higher ORR activity was obtained with the onset potential of 1.08 V vs. RHE and the limiting current density of 1.65 mA/cm2 for 40 wt. % Pt/VC/NP catalyst film. The ORR kinetic and thermodynamic parameters were calculated and compared with standard Pt/C literature values. © (2014) Trans Tech Publications, Switzerland.

The supportless PtRh nanoclusters (Pt3Rh NC) were prepared using formic acid reductant. High-resolution transmission electron microscopy (HRTEM) showed individual particle sizes less than 7 nm, and energy-dispersive X-ray (EDX) analysis confirmed a 3:1 ratio of Pt and Rh. The as-prepared Pt3Rh NC exhibited an improved activity and durability toward electrocatalytic oxidation of methanol (MOR) and possesses greater CO tolerance than conventional PtRu and other Pt-based MOR catalysts. For comparison, the Vulcan carbon supported (Pt3Rh NC/VC) catalyst was prepared under identical conditions and used for MOR. The supportless Pt3Rh NC catalyst possessed mass activity of 1392.5 mA mg-1 with an If/Ib ratio of 2.61, which is nearly 3-fold higher than the Pt3Rh NC/VC and also comparable to the benchmark MOR catalysts. The surface poisoning rate was found to be relatively smaller compared to the standard PtRu/C catalysts (δ = 0.0044% s-1). The activation energy for MOR was found to be 22.5 kJ mol-1. The durability study for 4000 potential cycles in an acidic solution showed that nearly 78% of mass activity has been retained. The supportless Pt3Rh NC has much improved activity and stability compared to both Pt3Rh NC/VC and standard PtRu MOR catalysts. Therefore, the supportless Pt3Rh NC could be seen as a potential electrocatalyst for methanol oxidation due to high activity, enhanced stability, and diminished poisoning of the Pt surface, which is stabilized in the presence of Rh in nanocluster morphology.

A novel Pt nanoparticle (Pt NP) embedded aminoclay/Nafion (Pt/AC/N) nanocomposite catalyst film was prepared for oxygen reduction reaction by sol-gel method. The prepared nanocomposite films were surface characterized using XRD and TEM and thermal stability was studied by TGA. The prepared film has firmly bound Pt NP and could exhibit an improved electro-reduction activity compared to vulcan carbon/Nafion supported Pt NP (Pt/VC/N). Moreover, the Pt/AC/N film possessed good stability in the acidic environment. The limiting current density of the Pt/AC/N film with 35.4 μg/cm 2 of Pt loading was found to be 4.2 mA/cm 2, which is 30% higher than that of the Pt/VC/N. The maximum H 2O 2 intermediate formation was found to be ∼1.6% and the reaction found to follow a four electron transfer mechanism. Accelerated durability test for 2000 potential cycles showed that ca. 78% of initial limiting current was retained. The results are encouraging for possible use of the Pt/AC/N as the free-standing electrocatalyst layer for polymer electrolyte membrane fuel cells. © 2012 American Chemical Society.

This work demonstrates the use of amino functionalized Mg-phyllosilicate clay/Nafion nanocomposite film embedded with Pt nanoparticles (Pt/AC/N) for catalyzing oxygen reduction reaction (ORR) in sulphuric acid medium. Pt/AC/N nanocomposite films were surface characterized using transmission electron microscope. Cyclic and linear scan voltammetry studies were carried out under hydrodynamic conditions taking rotating-ring disc electrode (RRDE) as the working electrode. The effects of clay content, Pt mass loading, electrode rotation rate, and temperature on the ORR kinetics were studied. The Tafel slopes were found to vary between 118 and 126mVdec -1 indicating a good ORR kinetics. The exchange current density values calculated after mass transfer correction ranged from 5.8×10 -7 to 2.4×10 -6Acm -2. From the RRDE disc currents, Koutecky-Levich plots were constructed and the ORR mechanism was found to follow a four electron path with minimum H 2O 2 formation of ∼1.6%. The effect of temperature on ORR kinetics was found at 25, 40, and 50°C. The energy of activation calculated to be 7.68kJmol -1 and comparable to the standard Pt/C catalyzed ORR systems. © 2012 Elsevier Inc.