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Low cathodic oxygen reduction reaction (ORR) efficiency is one of the important factors limiting the hydrogen fuel cells. Platinum can effectively reduce the ORR activation energy and improve the reaction rate; However, platinum's low reserves, versatility, and high price still limit its use in commercial, large-scale applications. It is very important to reduce the amount of Pt and improve the utilization rate and the stability of Pt-based catalyst. Here, an ultra-low Pt content catalyst Pt&Fe 2 O 3 /PM has been synthesized. The Pt content of the catalyst is only 4 wt%, and its nanoparticles are about 3 nm. Pt&Fe 2 O 3 /PM exhibit excellent ORR catalytic performance and longevity in acidic electrolyte. The ORR mechanism on Pt&Fe 2 O 3 /PM involves a direct four-electron path. The mass activity and specific activity of Pt&Fe 2 O 3 /PM is 4.8 and 10.3 times than that of commercial Pt/C, respectively. Furthermore, the catalyst's synthesis method is straightforward and amenable to scaling up, offering significant guidance for the creation of low-Pt catalysts. [Display omitted] • High dispersion low-Pt catalyst Pt&Fe 2 O 3 /PM was prepared by heat treatment. • The particle size of the Pt&Fe 2 O 3 /PM is ca. 3 nm, and the Pt content is ca. 4 wt%. • Pt&Fe 2 O 3 /PM has higher ORR activity and durability than commercial Pt/C. [ABSTRACT FROM AUTHOR]

Designing an electrocatalyst with low Pt content is an immediate need for essential reactions in low temperature fuel cell systems. In the present work, La0.9925Ba0.0075Al0.995Pt0.005O3 is aimed at using with low (only 0.5%) Pt doping as an electrocatalyst for oxygen reduction reaction (ORR). The low doping level renders exsolution of 1–2 nm nanoparticles with uniform dispersion upon reduction in H2/N2 at low temperatures. Pt exsolved perovskite oxides deliver significantly enhanced catalytic activity for ORR and improved stability in alkaline media. This study demonstrates that LaAlO3 with low noble metal content holds immense potential as an electrocatalyst in real fuel cell systems. [ABSTRACT FROM AUTHOR]

The kinetic of the oxygen reduction reaction (ORR) at the cathodes of polymer-electrolyte-membrane fuel cells (PEMFCs) has been demonstrated to be slow, which is one of the pivotal issues in developing PEMFCs. Within the current piece of research, by performing first-principles calculations, we introduce a Co-doped vacancy BN nanosheet (Co-HBN) as an efficacious noble metal-free electro-catalyst for the ORR process (ORRP) in fuel cells. The results demonstrate a rise in the energies of adsorption (or adhesion) onto the Co–N active site of these electrocatalysts in the order of O < OH < OOH < O 2 < H 2 O 2 < H 2 O on this electrocatalyst and there is a consistent change in the adsorption energies (E ads)for all oxygen-containing intermediates (OCIs). Based on the small and large thermodynamic driving force for the generation of H 2 O 2 and for reducing OOH into O∗ (or to 2OH∗), respectively, the four-electron route was more favorable in comparison with the 2e− route. Furthermore, with the largest value of ΔG for Co-HBN electrocatalyst, the final reduction step (OH∗ + H+ + e− → H 2 O + ∗) has been regarded as the rate-limiting step. The d-band center of Co was considerably distant from the Fermi level. The greater gap between the frontier orbitals suggested that the electrocatalyst is not conducive to the adsorption of OCIs, which shows that the onset potential is larger and ORR is high. • The catalytic activity of a series of Co-doped v-BN has been theoretically explored in the ORR. • O 2 molecule can be directly dissociated on the Co-doped v-BN with 4e pathway. • It is reacting more favorable for the ER mechanism of OH∗ to convert into H 2 O. • The ORR reaction was found to be thermodynamically favorable in the Co-doped v-BN. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) represent a breed of eco-friendly, weather-independent, decentralized power generation technologies, distinguished for their broad fuel versatility and superior electricity generation efficiency. At present, SOFCs are impeded by a lack of highly efficient oxygen reduction catalysts, a factor that significantly constrains their performance. The double perovskites LnBaCo2O5+δ (Ln = Lanthanide), renowned for their accelerated oxygen exchange and conductivity features, are widely acclaimed as a promising category of cathode catalysts for SOFCs. This manuscript offers a novel perspective on the physicochemical attributes of LnBaCo2O5+δ accumulated over the past two decades and delineates the latest advancements in fine-tuning the composition and nanostructure for SOFC applications. It highlights surface chemistry under operational conditions and microstructure as emerging research focal points towards achieving high-performance LnBaCo2O5+δ catalysts. This review offers a comprehensive insight into the latest advancements in utilizing LnBaCo2O5+δ in the field of SOFCs, presenting a clear roadmap for future developmental trajectories. Furthermore, it provides valuable insights for the application of double perovskite materials in domains such as water electrolysis, CO2 electrolysis, chemical sensors, and metal–air batteries. [ABSTRACT FROM AUTHOR]

High-porosity, crystalline, and surface-area-rich metal–organic frameworks (MOFs) may be employed in electrochemical energy applications for active catalysis. MOFs have recently been modified using secondary building blocks, open metal sites with large pore diameters, and functional ligands for electronic conductivity. They have the potential for excellent performance in fuel cell applications, and they have several possibilities to enhance the fundamental characteristics of mass and electron transportation. MOFs may be combined with other materials, such as solitary metal nanoparticles and carbon and nitrogen composites, to increase their catalytic efficacy, especially in oxygen reduction reaction (ORR). As a result, this study focuses on MOF derivatives for ORR applications, including porous carbon MOF, single metal MOF-derived composites, metal oxides, and metal phosphides. An efficient MOF electrocatalyst platform for ORR applications is presented, along with its prospects. These initiatives promote promising MOF electrocatalysts for enhancing fuel cell efficiency and pique curiosity for possible growth in subsequent research. [ABSTRACT FROM AUTHOR]

Graphene has been proposed as support or as co-support for Proton Exchange Membrane Fuel cells (PEMFCs) electrocatalysts due to its high electronic conductivity, corrosion stability and high specific surface area compared to common carbon blacks, such as Vulcan. Despite such outstanding properties, comprehensive studies on long-term stability of graphene-supported Oxygen Reduction Reaction (ORR) catalysts are still unavailable or limited. The stability of graphene as support is now studied and compared with carbon black in terms of electrochemical performance and degradation mechanisms. Catalytic layers with Pt/G were prepared and subjected to a set of three different Accelerated Stress Tests (ASTs): cycling at high potentials, Open Circuit Potential (OCP) holding and cycling at low potentials. This study aims to assess if and why graphene is a better candidate as support. The Pt/G catalyst outperformed the reference catalyst in all ASTs, delivering both higher electrochemical active surface area (ECSA) and ORR mass-specific activity. Such electrochemical performance was correlated with morphological evidences associated to the support itself and with Pt nanoparticles. • Stability of Pt/G was studied via three different degradation protocols and compared to Pt/H. • Potential cycling below 1 V promotes higher ORR mass-specific activity loss, among all ASTs. • Pt/G maintained higher ECSA and ORR activity than Pt/H upon the different types of ASTs. • Pt/G is considerably more stable than Pt/H despite observing a higher particle growth. [ABSTRACT FROM AUTHOR]

The rational construction and preparation of efficient, stable, and economic electrocatalysts for the oxygen reduction reaction (ORR) are necessary for fuel cells. In this work, we fabricated a porous carbon skeleton structure consisting of bimetallic organic framework (BMMOF)-derived N-doped microspheres linked with graphene oxide (GO) conducting network (denoted as UA-Co/RSC@NGF, where "UA" stands for ultrasound-assisted, "RSC" stands for resin microspheres, and "NGF" stands for N-doped graphene framework) as an efficient ORR catalyst by an ultrasound-assisted and one-step pyrolysis method. In this configuration, benefiting from the support of carbon microspheres and the strong synergistic coupling with GO, the structure of UA-Co/RSC@NGF is stabilized, and the large specific surface area enhances the density of active sites. With UA-Co/RSC@NGF as the catalyst, significant ORR properties were achieved with a high half-wave potential (E1/2, 0.90 V), an onset potential (Eonset, 1.03 V), and a large limited current density (5.37 mA cm−2). The durability and methanol resistance of UA-Co/RSC@NGF in alkaline media outperform commercially available Pt/C. This study may open a pathway for rationally designing multidimensional composite-structured carbon-based ORR catalysts for energy-related applications. [ABSTRACT FROM AUTHOR]

Graphene is a well-known two-dimensional material with a large surface area and is used for numerous applications in a variety of fields. Metal-free carbon materials such as graphene-based materials are widely used as an electrocatalyst for oxygen reduction reactions (ORRs). Recently, more attention has been paid to developing metal-free graphenes doped with heteroatoms such as N, S, and P as efficient electrocatalysts for ORR. In contrast, we found our prepared graphene from graphene oxide (GO) by the pyrolysis method under a nitrogen atmosphere at 900 °C has shown better ORR activity in aqueous 0.1 M potassium hydroxide solution electrolyte as compared with the electrocatalytic activity of pristine GO. At first, we prepared various graphene by pyrolysis of 50 mg and 100 mg of GO in one to three alumina boats and pyrolyzed the samples under a N2 atmosphere at 900 °C. The prepared samples are named G50-1B to 3B and G100-1B and G100-2B. The prepared GO and graphenes were also analyzed under various characterization techniques to confirm their morphology and structural integrity. The obtained results suggest that the ORR electrocatalytic activity of graphene may differ based on the pyrolysis conditions. We found that G100-1B (Eonset, E1/2, JL, and n values of 0.843, 0.774, 4.558, and 3.76) and G100-2B (Eonset, E1/2, and JL values of 0.837, 0.737, 4.544, and 3.41) displayed better electrocatalytic ORR activity, as did Pt/C electrode (Eonset, E1/2, and JL values of 0.965, 0.864, 5.222, and 3.71, respectively). These results display the wide use of the prepared graphene for ORR and also can be used for fuel cell and metal–air battery applications. [ABSTRACT FROM AUTHOR]

Sluggish oxygen reduction reaction (ORR) of electrodes is one of the main challenges in fuel cell systems. This study explored the kinetics of the ORR reaction mechanism, which enables us to understand clearly the electrochemical activity of the electrode. In this research, electrocatalysts were synthesized from platinum (Pt) catalyst with multi-walled carbon nanotubes (MWCNTs) coated by three polymers (polybenzimidazole (PBI), sulfonated tetrafluoroethylene (Nafion), and polytetrafluoroethylene (PTFE)) as the supporting materials by the polyol method while hexachloroplatinic acid (H2PtCl6) was used as a catalyst precursor. The oxygen reduction current of the synthesized electrocatalysts increased that endorsed by linear sweep voltammetry (LSV) curves while increasing the rotation rates of the disk electrode. Additionally, MWCNT-PBI-Pt was attributed to the maximum oxygen reduction current densities at −1.45 mA/cm2 while the minimum oxygen reduction current densities of MWCNT-Pt were obtained at −0.96 mAcm2. However, the ring current densities increased steadily from potential 0.6 V to 0.0 V due to their encounter with the hydrogen peroxide species generated by the oxygen reduction reactions. The kinetic limiting current densities (JK) increased gradually with the applied potential from 1.0 V to 0.0 V. It recommends that the ORR consists of a single step that refers to the first-order reaction. In addition, modified MWCNT-supported Pt electrocatalysts exhibited high electrochemically active surface areas (ECSA) at 24.31 m2/g of MWCNT-PBI-Pt, 22.48 m2/g of MWCNT-Nafion-Pt, and 20.85 m2/g of MWCNT-PTFE-Pt, compared to pristine MWCNT-Pt (17.66 m2/g). Therefore, it can be concluded that the additional ionomer phase conducting the ionic species to oxygen reduction in the catalyst layer could be favorable for the ORR reaction. [ABSTRACT FROM AUTHOR]

Fe/N−C electrocatalysts were synthesized using iron chloride, ammonium chloride, glycine, and acetylene black by pyrolysis at 900 °C under nitrogen atmosphere. Acid leaching process successfully removed non‐bonded Fe which confirmed by X‐ray Diffraction (XRD) analysis. Deconvolution of Raman spectra showed that Fe1−NC had a high ID/IG value of 1.37 due to the presence of defect sites and disordered carbon structure. The calculation result showed that higher Fe loading leads to the carbon structure rearrangement into graphitic structure, thus reducing the ID/IG to 1.06. The cyclic voltammetry (CV) test of Fe1−NC shows the best catalytic performance for oxygen reduction reaction (ORR) compared to higher Fe‐loading samples. Rearrangement in the carbon structure into the more graphitic led to active sites decrease, thus resulted in a decrease of IORR from 4.6 to 1.7 μA for Fe1−NC and Fe20−NC. This study indicates that optimum iron loading could be an essential factor in improving catalyst performance. [ABSTRACT FROM AUTHOR]

Electrocatalysts play a pivotal role in advancing proton-exchange membrane fuel cell (PEMFC) for hydrogen energy applications. In this study, we investigate a novel PtCu/C N electrocatalyst synthesized via a gram-scale synthesis approach, which demonstrates remarkable activity and stability in the oxygen reduction reaction (ORR). The catalyst's effectiveness stems from its unique structure, combining bimetallic nanoparticles (NPs) and an N-doped carbon support. Employing identical location transmission electron microscopy (IL-TEM) imaging, we observe significant NP structure reorganization upon activation influenced by the upper limiting potential. Notably, the PtCu/C N catalyst activated to 1.0 V surpasses the United States Department of Energy (DOE) target for ORR activity by 3.3-fold. These findings underscore the potential of this catalyst in enhancing the performance of PEMFCs, marking a significant advancement in hydrogen energy technology. [Display omitted] • Catalyst's effectiveness attributed to unique structure of bimetallic NPs and N-doped support. • Vital reorganization of NPs occurs under the upper limiting potential of activation. • PtCu/C N catalyst activated to 1.0 V surpasses DOE target for ORR activity by 3.3-fold. • IL-TEM method comes to the rescue in assessing NPs' reorganization. • Findings highlight potential of bimetallic catalyst in enhancing PEMFC performance. [ABSTRACT FROM AUTHOR]

High-efficiency catalysts are required for the oxygen reduction reaction (ORR) in fuel cell applications. Herein, we present a novel hybrid material that is based on uniformly deposited nanoscale molybdenum phosphide (Mo x P y) nanoparticles on the structure of graphene nanolayers doped with phosphorus atoms (PG). With a positive onset potential of only −0.046 V and a half-wave potential value of roughly −0.17 V (vs. Ag/AgCl), the obtained hybrid showed good catalytic activity for ORR in 0.1 M KOH electrolyte. It also demonstrated remarkable durability for oxygen reduction reaction in 0.1 M KOH electrolyte when compared to state-of-the-art Pt/C material. The excellent ORR performance can be correlated to the development of a highly conducting microporous structure with highly active sites, which in turn encourages optimal adsorption of intermediates during the ORR process and thus enhances the catalytic process. This work can open a new path for the growth of promising highly efficient catalysts for affordable fuel cell applications. [Display omitted] • Uniform Mo x P y nanoparticles dispersed P-doped G was prepared by a facile route. • The hybrid offered high catalytic performance for ORR, close to Pt/C. • The synergistic effect from Mo x P y and P-doped Gr produced enhanced ORR performance. • The hybrid showed much better durability and methanol tolerance than Pt/C. [ABSTRACT FROM AUTHOR]

The slow reaction rates observed in the Oxygen Reduction Reaction (ORR) pose a significant obstacle in advancing fuel cell technology. Consequently, ORR plays a pivotal role in determining the operational efficiency of fuel cell and energy storage systems. Accordingly, the synthesis of a cathodic electrocatalyst with high efficiency has become an attractive topic for researchers. In this empirical study, three trimetallic electrocatalysts are synthesized and electrochemically appraised. By introducing three lanthanides, namely Gadolinium (Gd), Samarium (Sm), and Europium (Eu), into CuFeZIF-8, new composites successfully are synthesized as Cu@FeLn (Eu, Sm, and Gd)-N-C. These functional materials find application in the context of the ORR and supercapacitor technologies. In order to enhance stability, control surface area, and prevent agglomeration during high-temperature pyrolysis, the silicon cover protection technique is employed. The primary objective in this investigation is to assess the influence of mSiO 2 coating on the electrochemical parameters of these electrocatalysts. To characterize the fabricated samples, seven characterization tests are utilized. Electrochemical measurements are conducted employing a three-electrode cell configuration within an alkaline environment. The results illustrated that the Cu@FeGd-N-C sample, with an onset potential of −0.043 V vs. Ag/AgCl, exhibited the best ORR performance. Also, the electron transfer number of Cu@FeSm-N-C was computed as 3.56. The half-wave potentials of Cu@FeSm-N-C, Cu@FeEu-N-C, and Cu@FeGd-N-C were found to be −0.34, −0.23, and −0.18 V vs. Ag/AgCl, respectively. A less negative half-wave potential typically suggests superior performance, signifying a lower overpotential requirement for the ORR process. The specific capacitance for Cu@FeGd-N-C electrode at 1 A/g was determined as 144.4 F g−1. The inclusion of lanthanides, Fe, and Cu into ZIF-8 is observed to notably improve both catalytic activity and electron transfer. Also, the outcomes showed that mesoporous silica-protected pyrolysis could be a useful strategy for improving the efficiency of energy conversion and energy storage equipment. [Display omitted] • By introducing three lanthanides into CuFeZIF-8, new composites are synthesized and evaluated. • To prevent irreversible fusion, the strategy of applying an mSiO2 coating is implemented. • The synthesized catalysts were used for two applications: energy conversion and storage. • The best ORR performance is associated with the Cu@FeGd-N-C sample, with an onset potential of −0.043 V vs. Ag/AgCl. • The Cu@FeGd-N-C electrode exhibited a specific capacitance of 144.4 F g−1 at a current density of 1 A/g. [ABSTRACT FROM AUTHOR]

This work proposes a cost-effective strategy to massively synthesize high-efficiency ORR electrocatalyst. [Display omitted] • A novel type of composite Co/N C was prepared. • A potential strategy was proposed to massively synthesize ORR catalysts. • High ORR activity of Co/N C triggered by Co-N heteroatomic interface. • The high stability of Co/N C in 0.1 M KOH. The development of high-efficiency and low-cost oxygen reduction electrocatalysts have become an urgent need to push fuel cells into practical application. Herein, an effective electrocatalyst Co/N C was successfully constructed, which was derived from abundant peanut shells, obtained by doping with cobalt ions and pyrolyzing in NH 3 atmosphere. Due to the abundant Co-N active sites triggered by Co-N heteroatomic interface, the prepared electrocatalysts present excellent oxygen reduction reaction (ORR) performance with more positive half-wave potential (E 1/2 = 0.83 V), incremental limiting current density (J L = 5.45 mA cm−2), higher durability and stronger resistance to methanol, which is superior to that of Pt/C (E 1/2 = 0.81 V and J L = 5.19 mA cm−2). This work proposes a potential strategy to synthesize efficient ORR electrocatalysts to instead of Pt-based catalysts. [ABSTRACT FROM AUTHOR]

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Herein, molybdenum disulfide nanoflakes decorated copper phthalocyanine microrods (CuPc-MoS 2) are synthesized via two step simple hydrothermal method. The as synthesized hybrid along with pure molybdenum disulfide (MoS 2) nanoflower and pure copper phthalocyanine (CuPc) microrods are well characterized by various techniques that confirm phase, morphology, elemental compositions etc. Next, electrocatalytic oxygen reduction reaction towards fuel cell is investigated in alkaline medium and obtained results proclaim that our CuPc-MoS 2 heterostructure outperforms the other two constituent materials. Efficient oxygen reduction is achieved following four electron pathway by CuPc-MoS 2 whereas partial reduction is done through two electron process by CuPc and MoS 2 separately. Long-time durability test reveals almost 97.6% retention after 8000s that eventually dictate us that CuPc-MoS 2 heterostructure can be the efficient cathode electrocatalyst for future generation fuel cell. [Display omitted] • Hierarchical growth of MoS 2 on CuPc rod is formed using low temperature facile route. • Enhanced electrocatalytic ORR of CuPc-MoS 2 is observed than bare counterparts. • Long-time durability test reveals almost 97.6% retention after 8000s for CuPc-MoS 2. • Structure activity relationship and active edge sites play role for enhanced ORR. [ABSTRACT FROM AUTHOR]

The structurally ordered PtM with surface coating layers strategy has drawn increasing attention. In this work, we synthesize a structurally ordered PtFe@NC-X-PDA catalyst modified with nitrogen-doped carbon coating layers by confined space annealing strategy. Compared with the current commercial Pt/C catalyst, the structurally ordered PtFe@NC-X-PDA catalyst shows better catalytic activity and stability. Especially, the mass activity and specific activity of the synthesized PtFe@NC-0.06-PDA sample with the optimized poly-dopamine feeding mass content (0.06 g) exhibit 9.95 and 11.53 times higher than that of commercial Pt/C catalyst. In addition, after 20,000 CV cycles, the PtFe@NC-0.06-PDA sample achieves the minimum activity loss (7%). The PtFe alloy catalyst with the different thickness NC shell (PtFe@NC-X-PDA) possesses the enhanced ORR activity and stability owing to the protection of nitrogen carbon shell (NC) and the strong electronic interaction of the ordered PtFe NPs. The improved ORR activity and stability of the structurally ordered PtFe@NC-X-PDA catalyst provide a promising direction for the development of fuel cells. Herein, we have successfully achieved precise modulation of the nitrogen doped carbon coating layers thickness in situ and simultaneously regulation the interfacial or chemical ordering energy at the atomic level that possess enhanced catalytic ORR activity and stability. [Display omitted] • A confined space annealing strategy of poly-dopamine was proposed to improve the performance of PtFe nanoparticles. • The level of alloy degree is turned by the poly-dopamine feeding mass content. • The protection from NC shell and ordered structure collectively guarantee the stability of the catalyst. • The PtFe@NC-0.06-PDA catalyst with suitable NC shell thickness possesses enhanced oxygen reduction performance. [ABSTRACT FROM AUTHOR]

Developing cost‐effective non‐precious metal electrocatalysts (NPMCs) for the sluggish oxygen reduction reaction (ORR) is critical for the large‐scale application of metal‐air battery and fuel cell technologies. Herein, we present an effective Mn/Zn bimetal organic frameworks (MOFs)‐based strategy to synthesize an efficient manganese (Mn) and nitrogen (N) co‐doped porous carbon electrocatalyst with atomically dispersed N‐coordinated single Mn moieties (Mn‐Nx) for ORR catalysis. This strategy involves the adsorption of Mn ions into the Mn/Zn bimetal MOFs followed by the subsequent pyrolysis in Ar and then activation in NH3. Owing to the atomically dispersed Mn‐Nx sites, the large specific surface area and the high content of graphitic‐N, the resulting electrocatalyst shows a superior ORR activity with a half‐wave potential of 0.885 V and an outstanding electrochemical durability in alkaline electrolyte outperforming commercial Pt/C, and it also exhibits a superior performance for an assembled primary Zn–air battery. This work offers a new prospect for the synthesis of MOFs‐derived highly efficient NPMCs for ORR. [ABSTRACT FROM AUTHOR]

Integrating ultralow-Pt alloy into nanocarbons: Ternary PtCoNi alloy with ultralow Pt loading integrated in nitrogen-doped nanocarbon architecture endows an excellent half-cell activity and single-cell performance. [Display omitted] Developing efficient platinum (Pt)-based electrocatalysts is enormously significant for fuel cells. Herein, we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon architecture for efficient oxygen reduction reaction. This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mg pt −1 at the potential of 0.9 V vs. RHE with a negligible stability decay after 10,000 cycles. More importantly, this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mg Pt −1 cathode and remarkable durability after 30,000 cycles in single-cell. Experimental and theoretical investigations reveal that a highly strained Pt structure with an optimal Pt-O binding energy is induced by the incorporation of Co/Ni into Pt lattice, which would account for the improved reaction kinetics. The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt component is responsible for the enhanced catalytic activity. Meanwhile, the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management. This work may provide significant insights in designing the low-Pt integrated electrocatalysts for fuel cells and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] Designing efficient electrocatalysts for the oxygen reduction reaction (ORR) is crucial to enhance the energy efficiencies of metal-air batteries and fuel cells. Palladium (Pd) catalysts show great potential due to their high intrinsic activity towards ORR but suffer from inferior durability. Here, we aim to employ tin oxide (SnO 2) supports to tailor the lattice strain and electron density of Pd catalysts to enhance their ORR performance. By using electrospinning and solvothermal techniques, a hierarchical Pd/SnO 2 hybrid catalyst was facilely synthesized with Pd nanoparticles anchored onto both the inside and outside walls of nanotube-like SnO 2 supports. Owing to the SnO 2 supports and the endowing metal-support interactions, tensile-strain and electron-rich features were both verified for the Pd nanoparticles in the Pd/SnO 2 catalyst. In comparison, no such features were found for the Pd nanoparticles in the Pd/C catalyst. As a consequence, the Pd/SnO 2 hybrid catalyst exhibits 2.5-times higher mass activity than the Pd/C catalyst and greatly improved durability with a current decay of 4% loss over 50 h compared with that (18%) of the Pd/C catalyst. [ABSTRACT FROM AUTHOR]

The unique chemical and physical properties of graphene and its derivatives (graphene oxide, heteroatom‐doped graphene, and functionalized graphene) have stimulated tremendous efforts and made significant progress in fuel cell applications. This review focuses on the latest advances in the use of graphene‐based materials in electrodes, electrolytes, and bipolar plates for fuel cells. The understanding of structure‐activity relationships of metal‐free heteroatom‐doped graphene and graphene‐supported catalysts was highlighted. The performances and advantages of graphene‐based materials in membranes and bipolar plates were summarized. We also outlined the challenges and perspectives in using graphene‐based materials for fuel cell applications. [ABSTRACT FROM AUTHOR]

Non-noble metal electrocatalysts for oxygen reduction reaction are essential for the sustainability and cost reduction of energy conversion devices. However, the performance of non-noble metal catalysts is far inferior to that of platinum-based catalysts. It remains a challenge to synthesize high-performance non-noble metal catalysts using simple methods. Iron and copper are the core elements of hemoglobin and hemocyanin, which are the main components of oxygen carried in animals. Based on the above inspiration, a novel Fe and Cu bimetallic mixed porous carbon material was synthesized by a one-step method. Our catalyst Fe-Cu–N/C-F-1.5 had a porous structure, and its specific surface area is 625 m2 g−1. Fe–Cu–N/C–F-1.5 exhibited an excellent electrochemical characteristic with an initial potential of 0.98 V and a half-wave potential of 0.85 V, which could achieve better electrochemical activity than commercial Pt/C. This work provides a general approach for the rational design of transition metal and heteroatom mixed porous carbon electrocatalysts. A Fe- and Cu-doped carbon catalyst, Fe–Cu–N/C–F-1.5, is prepared from melamine, polytetrafluoroethylene (PTFE), and FeCl3, (CH3COO)2Cu•H2O by a one-pot method. Fe–Cu–N/C–F-1.5 with a porous structure and its specific surface area is 625 m2 g−1. Fe–Cu–N/C–F-1.5 shows good catalytic performance in ORR processes. The ORR half-wave potential of Fe–Cu–N/C–F-1.5 is positively shifted by 35 mV compared with that of commercial Pt/C. [ABSTRACT FROM AUTHOR]

In this paper, CoMn 2 O 4 /NC nanocomposites were synthesized via a facile ionothermal synthesis route, and their electrocatalytic performance for oxygen reduction reaction (ORR) was investigated in a direct glucose alkaline fuel cell (DGAFC). The CoMn 2 O 4 spinel supported on nitrogen-doped carbon was successfully synthesized with the assistance of the ionic liquid [C 6 mim]Cl. The nanocomposite exhibited excellent electrocatalytic activity towards ORR. Especially, CoMn 2 O 4 /NC achieved a half wave potential of 0.81 V (vs RHE) and a maximum diffusion limiting current density of 5.2 mA cm−2, that are very close to commercial Pt/C catalyst (E 1/2 = 0.83 V vs RHE, J d = 5.0 mA cm−2). In addition, the catalytic performance of CoMn 2 O 4 /NC was investigated in DGFC. The fuel cell with a CoMn 2 O 4 /NC air cathode achieved a peak power density of 23.72 W m−2, which was even superior to that with a commercial Pt/C air cathode. This work revealed that ionic liquid is a viable reaction medium for preparation of catalyst with robust activity. [Display omitted] • CoMn 2 O 4 /NC nanostructure was prepared via an ionothermal method. • The nanocomposite exhibited excellent electrocatalytic ability for ORR. • The fabricated material was employed in a DGAFC. • Ionothermal synthesis method is facile to fabricate novel catalysts. [ABSTRACT FROM AUTHOR]

The development of metal-free carbon-based catalysts for alkaline fuel cells has been the subject of current interest, because of the low cost and improving fuel cell efficiency. Particularly, nitrogen-doped carbon shows prominent results. Here, we show an oxygen reduction reaction (ORR) activity of nitrogen-doped graphene-like carbon materials (N-GLC) prepared by heating bagasse-derived carbon and melamine in a 1:15 ratio. The N-GLC catalyst displays excellent electro-catalytic activity towards the ORR with an onset potential of 0.92 V vs. reversible hydrogen electrode (RHE) in alkaline media (0.1 M KOH). Moreover, the half-wave (E1/2) potential 0.83 V is almost the same compared to Pt-C (40 wt%) catalyst and the diffusion limiting current of 4 mA cm–2. The rotating ring disc experiment showed a four-electron pathway (n = 3.65) with the moderate peroxide ( HO 2 - ) yield. Due to its promising ORR activity and long-term electrochemical stability, N-GLC catalyst is used in alkaline anion exchange membrane fuel cell (AEMFC) as a single cell, about 6 mW cm–2 peak power density was achieved at the load current density of ~20 mA cm–2. So the N-GLC can be a cheap alternative ORR catalyst for AEMFC applications. [ABSTRACT FROM AUTHOR]

To accelerate the commercialization of fuel cells, many efforts have been made to develope highly active and durable Pt-based catalyst for oxygen reduction reaction (ORR). Herein, PtCu porous nanowires (PNWs) with controllable composition are synthesized through an ultrasound-assisted galvanic replacement reaction. The porous structure, surface strain, and electronic property of PtCu PNWs are optimized by tuning composition, which can improve activity for ORR. Electrochemical tests reveal that the mass activity of Pt 0.5 Cu 0.5 PNWs (Pt/Cu atomic ratio of 1:1) reaches 0.80 A mg Pt −1, which is about 5 times higher than that of the commercial Pt/C catalyst. Notably, the improved activity of the porous nanowire catalyst is also confirmed in the single-cell test. In addition, the large contact area with the carrier and internal interconnection structure of Pt 0.5 Cu 0.5 PNWs enables them to exhibit much better durability than the commercial Pt/C catalyst and Pt 0.5 Cu 0.5 nanotubes in accelerated durability test. [Display omitted] • Porous nanowires are prepared by ultrasound-assisted galvanic replacement method. • The ultrasound plays an important role in the formation of porous structure. • PtCu porous nanowires (PNWs) show highly activity and durability for ORR. • The combined advantages of PtCu PNWs lead to enhanced ORR performances. • The porous nanowires show higher activity and stability than the hollow nanotubes. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated the temperature effect of our previously developed topotatic catalysis for the formation of Mn0.005Co2.995O4 (MnCoO) spinel nanoparticles. Topotatic catalysis induces spinel MnCoO nanoparticles through the redox reaction of the metal cation (Co2+ and Mn2+) on the Co(OH)2 nanosheet surface, acting as a growth template. This study particularly elucidates the temperature effect on spinel MnCoO nanoparticles' size, morphology, and crystallinity based on their electrocatalytic performance in an oxygen reduction reaction (ORR). We found that lower temperature produces an amorphous phase, whereas higher temperature induces a large aggregate. We obtained the monodispersed MnCoO nanocubes at approximately 90°C, exhibiting the best ORR performance with an electron‐transfer number of 3.86. [ABSTRACT FROM AUTHOR]

Metal nitrogen-carbon catalysts have become a promising alternative to platinum-based catalysts in fuel cells due to their high stability and platinum-like activity. However, the corrosion and deactivation of active sites in the solution still restrict the inherent reaction kinetic rate. For this reason, it is important to stabilize the catalyst through a controllable doping strategy to obtain high activity catalysts for oxygen reduction reactions (ORR). Herein, the pyrolysis strategy is demonstrated in the synthesis of iron-based catalysts co-doped with nitrogen and biomass-derived phosphorus (denoted as N, P-Fe/C), and the pore size of the catalyst is mostly distributed at 1 nm or 50 nm, respectively. The half-wave potential (0.893 V) and the current density (4.05 mA cm−2) at 0.85 V of the catalyst exceed those of the commercial Pt/C. The remarkable ORR performance can be attributed to its distinct hierarchical pore structure, the modulation effect of nitrogen and phosphorus co-doping on the carbon matrix, and the combined effect of the FeNx active sites, which improves the accessibility of reactants and accelerating the absorption/desorption of the reaction intermediate, thereby increasing reaction rates. And N, P-Fe/C has great potential as a promising substitute for platinum-based catalysts. [ABSTRACT FROM AUTHOR]

Designing highly active and durable oxygen reduction reaction (ORR) electrocatalysts is essential for developing efficient proton-exchange membrane fuel cells (PEMFCs). In this work, ordered PtCuNi/C nanoparticles (NPs) were synthesized using an impregnation reduction method. This study shows that the incorporation of Ni in ordered PtCu/C can effectively adjust the electronic structure of Pt, thereby optimizing oxygen binding energy for the ORR. The obtained intermetallic ordered PtCuNi/C NPs significantly improved ORR activity and durability compared to ordered PtCu/C. Specifically, PtCu 0 · 5 Ni 0 · 5 /C-700 shows a mass activity of 1.29 ​A ​mg Pt −1 ​at 0.9 ​V vs. reversible hydrogen electrode (RHE), which is about 9.2 times higher than that of commercial Pt/C. PtCu 0.5 Ni 0.5 /C-700 is also shown to be competent cathode catalyst for a single-cell system exhibiting high power density (461 ​mW ​cm−2). This work demonstrates that ordered PtCu 0 · 5 Ni 0 · 5 /C-700 can be used as a highly active and durable ORR catalyst in PEMFCs. The chemically ordered PtCuNi/C nanoparticles (NPs) were synthesized using an impregnation reduction method. Incorporation of Ni in ordered PtCu/C can effectively adjust the electronic structure of Pt, thereby optimizing electrochemical performance for the ORR. Image 1 • The PtCuNi/C ternary intermetallic catalyst was synthesized using an impregnation reduction method. • Incorporation of Ni in ordered PtCu/C can effectively adjust the electronic structure of Pt. • The mass activity of PtCu 0 · 5 Ni 0 · 5 /C-700 is 9.2 times that of commercial Pt/C. • The MEA using PtCu 0 · 5 Ni 0 · 5 /C-700 exhibites high power density of 461 ​mW ​cm−2 in a single-cell system. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) electrocatalysts derived from biomass have become one of the research focuses in hetero-catalysis due to their low cost, high performance, and reproducibility properties. Related researches are of great significance for the development of next-generation fuel cells and metal-air batteries. Herein, the preparation methods of various biomass-derived catalysts and their performance in alkaline, neutral, and acidic media are summarized. This review clarifies the research progress of biomass carbon-based electrocatalysts for ORR in acidic, alkaline and neutral media, and discusses the future development trends. This minireview can give us an important enlightenment to practical application in the future.

• α-MnO 2 nanorods have been in-situ supported on 3D-G via a facile hydrothermal method. • α-MnO 2 nanorods are evenly deposited on 3D-G surface which possesses more defects. • The synergistic interaction between α-MnO 2 nanorods and 3D-G improve ORR performance. • α-MnO 2 /3D-G catalyst exhibites excellent activity and durability for ORR in MFCs. Magnesium-air fuel cells are considered as a potential energy conversion device owing to a high theoretical specific capability, economic viability and environmental friendliness. In this work, α-MnO 2 nanorods are supported on three-dimensional graphene (3D-G) which is fabricated with coal tar pitch as the carbon precursor and MgO as the template via hydrothermal reaction. The synergistic interactions between α-MnO 2 nanorods and 3D-G improve the activity and durability performance for oxygen reduction reaction in 0.1 mol L−1 KOH solution. α-MnO 2 /3D-G exhibits a high half-wave potential (0.81 V) and superior to α-MnO 2 /C (0.72 V) and α-MnO 2 /rGO (0.76 V), and close to 20 wt% Pt/C (0.83 V). α-MnO 2 /3D-G also possesses higher durability than commercial Pt/C. Furthermore, the magnesium-air fuel cells based on α-MnO 2 /3D-G, air-cathode display the peak power density (106.2 mW cm−2), and continuously durability (discharge for 16 h at 50 mA cm−2 with the mere decay of cell voltage by 7.6%). These results prove that α-MnO 2 /3D-G catalyst with high activity and durability can be a promising electrocatalyst in magnesium-air fuel cells. [ABSTRACT FROM AUTHOR]

Reducing the consumption of precious Platinum (Pt) metal by alloying with other transition metals or searching a new low cost, Pt‐free catalyst with the activity and durability higher than the state‐of‐the‐art Pt/C catalyst are the two possible approaches to accelerate the practical application of low temperature fuel cells. Herein we investigate the oxygen reduction reaction (ORR) electrocatalytic activity (1023 μA cm−2.Pt; 5 times higher than commercial Pt/C) and the corrosion stability of novel "Pt skin@PdPt" nanostructures in acidic media. An interesting trend of increment in the ORR activity with durability cycles has been found indicating a systematic surface rearrangement in "Pt skin@PdPt". A systematic enhancement in the ORR activity from an initial value of 1023 μA cm−2.Pt to 1448 μA cm−2.Pt after 30,000 durability cycles has been observed indicating stable nature of low Pt content Pt skin@PdPt electrocatalyst. More than seven times (1448 μA cm−2.Pt) higher activity against the state‐of‐the‐art Pt/C catalyst has been seen with an electrochemical surface area (ECSA) of ∼97 m2 g−1.Pt, even after 30,000 potential cycles. [ABSTRACT FROM AUTHOR]

Development of efficient electrocatalysts for oxygen reduction reaction (ORR) from resource‐abundant, eco‐friendly, and low‐cost materials is important for environmental‐friendly fuel cells. In this work, N, P, S/Fe‐codoped carbon (FBC−Fe) with hierarchical porous structure was successfully prepared by the simple pyrolysis of feculae bombycis (FB) in the presence of ferric nitrate and followed by an acid etching process. FBC−Fe exhibits an excellent long‐term durability and a remarkable methanol‐resistance as well as a high electrocatalytic activity (Eonset: 0.92 V vs RHE, E1/2: 0.81 vs RHE, and electron transfer number: 4.1) comparable to commercial platinum–carbon (Pt/C, 20 wt.%) catalysts for the ORR in alkaline media. This low‐cost and simple approach provides a straightforward route to synthesize excellent electrocatalysts for ORR from biomass. [ABSTRACT FROM AUTHOR]

Several studies relying on the improvements to the important oxygen reduction reaction (ORR) activity for increasing the performance of fuel cells have been reported. However, the application of catalyst conditions used for realizing the excellent activity in a half‐cell to a single‐cell does not guarantee the translation of the excellent performance. Therefore, we investigated the performance characteristics of various types of commercially available catalysts, including alloy catalysts, and compared the trends between the half‐cells and single‐cells using linear scan voltammetry (LSV), polarization curves (IVP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. Furthermore, regression analysis was performed to identify the influential factors for examining the complex relationship between the half‐cell and single‐cell performance parameters. The study reveals, that it is highly challenging to express the performances of the catalyst and single‐cell using isolated factors. Additionally, even though the measured activity of the catalyst in a half‐cell is higher than that in the other half‐cells, the difference does not manifest significantly in the single‐cell when the conditions required for its activity are not optimized, indicating that the overall performance of the fuel cell membrane electrode assembly (MEA) is not determined solely by the catalyst. [ABSTRACT FROM AUTHOR]

Herein a pristine Cu(II)-MOF has been synthesized that showed fascinating structural features and Kagome net topology consisting of trigonal and hexagonal pores. The electrochemical studies revealed excellent electrocatalytic behaviour of the MOF towards ORR and shows extreme stability in electrochemical environment. [Display omitted] We have synthesized a new Cu(II)-based MOF, that shows a two-dimensional structure which is linked through elaborate H-bonding interactions resulting in a three-dimensional supramolecular structure. Cyclic voltametric studies demonstrate good electrocatalytic behavior with lowering the onset potential to 0.56 V. From LSV, the catalyst was found to produce high polarization current density at 0.1 V/s scan rate. The reported Cu-MOF represents an excellent Platinum group metal free electrocatalyst that exhibits an outstanding and stable electrocatalytic activity toward 4e-reduction of O 2 , facilitates the catalytic process in the fuel cell in a cost-effective manner and can play a vital role in ORR. [ABSTRACT FROM AUTHOR]

The design of a new electro-catalyst with rich active sites, sufficient surface areas, low cost, and excellent stability for promoting the oxygen reduction reaction (ORR) efficiency is a crucial research topic in the fuel cell's application. Herein, the successful preparation of 2D WS 2 and MoS 2 functionalized NiO nanoparticles onto the surface of nanodiamond and carbon support is reported. The effect of WS 2 and MoS 2 doping on nickel oxide/nanodiamond activity supported carbon composites (NiO/ND/C) as electro-catalysts for oxygen reduction reaction in an alkaline medium was evaluated. The combination of activated carbon with sp2 hybridization and nanodiamond with sp2 and sp3 hybridization allows for better materials support conductivity. All prepared electro-catalysts exhibit good electrochemical activity towards ORR. It's noticed that the most efficient electro-catalyst for ORR among all the prepared composites is WS 2 /NiO/ND/C, which exhibits the highest current density of −7.47 mA·cm−2 at a rotating speed of 2500 rpm and a retention stability of 94.3 % after 100-repetitive cycles. Moreover, the WS 2 /NiO/ND/C composite forces the ORR reaction through the direct four-electron pathway. This work spotlights the effect between the electronegative oxygen atoms, the electropositive Mo and W atoms, and the synergistic effect between WS 2 and carbon support. All this information confirms that the as-reported WS 2 /NiO/ND/C nanocomposite may be considered a hopeful cathodic electrode for ORR catalysis as an alternative catalyst for platinum-based ones. [Display omitted] • A support containing activated carbon and nanodiamond was prepared. • The activated carbon and nanodiamond support was functionalized with NiO nanoparticles (NiO/ND/C). • The compound was further functionalized with transition metal dicalcogenides namely WS 2 and MoS 2. • These composites were tested as electro-catalysts for oxygen reduction reaction (ORR). • WS 2 /NiO/ND/C exhibits the highest current density of –8.27 mA.cm–2 and a retention stability of 94.3%. [ABSTRACT FROM AUTHOR]

A cathode catalyst possessing increased activity for oxygen reduction reaction (ORR) with superior durability is greatly required for polymer electrolyte membrane fuel cells (PEMFCs). Although Platinum (Pt) alloys have been widely studied for ORR, their real time application in fuel cells still remains a challenging task. Chemically ordered Pt alloys have attracted widespread attention due to the unique electronic and geometric factors that boost their electrocatalytic activity. Therefore, it is highly urgent to fabricate such ordered alloys as efficient cathode catalysts in fuel cells. Herein we report for the first time, a one-step solid-state method for the preparation of Pt 3−x Co 0.5+y Ni 0.5+y /C (x = 0, 1, 2; y = 0, 0.5, 1) nanoparticles on carbon support. Different compositions of this catalyst were studied and Pt 2 Co 1 Ni 1 /C was found to be the optimal, best performing catalyst both under half-cell and full-cell conditions. Interestingly, the mass activity of Pt 2 Co 1 Ni 1 /C was found to be seven times higher than that of commercial Pt/C in an acidic medium, achieving the Department of Energy (DOE) target for 2025. Moreover, a retention in mass activity after 50k cycles confirmed the superiority of this catalyst in effectively catalysing ORR reactions under an acidic medium. Importantly, the peak power density achieved by Pt 2 Co 1 Ni 1 /C under actual PEMFC operating conditions outperforms the commercially used Pt/C. Thus, this work provides a new approach for the simple and scalable synthesis of optimal cathode catalysts for fuel cells, opening up new dimensions in the field of energy research. • One-step solid-state method for the preparation of Pt 3−x Co 0.5+y Ni 0.5+y /C (x = 0, 1, 2; y = 0, 0.5, 1) nanoparticles. • I m of Pt 2 Co 1 Ni 1 /C found to be seven times higher than that of commercial Pt/C in an acidic medium. • Retention in mass activity after 50k cycles. • The peak power density of Pt 2 Co 1 Ni 1 /C under PEMFC conditions outperforms Pt/C. [ABSTRACT FROM AUTHOR]

A simple approach towards preparation of non-noble metal electrocatalyst for oxygen reduction reaction in low temperature fuel cells has been necessity for a sustainable green technology. Herein, a cost-effective and facile method of preparation of TiC@N-doped graphene like carbon nanocomposite (TiC@NC) has been discussed. The composite structure of as-prepared TiC@NC was confirmed using structural analysis and morphological studies. Interestingly, the optimized TiC@NC(0.2)-800 electrocatalyst shows remarkable oxygen reduction reaction (ORR) kinetics with better onset potential +1.08 vs RHE and significant current density of 4.8 mA/cm2 in alkaline medium. Further, obtained catalyst exhibits four electron transfer mechanism similar to Pt-based electrocatalysts. Additionally, TiC@NC(0.2)-800 shows better mass activity (∼410 mA/mg) as compared to other compositions. Moreover, the single step kinetics mechanism has been seen due to lower (<5%) peroxide yield. The relatively lower charge transfer resistance at electrode/electrolyte interface of TiC@NC (0.2)-800 electrode supports for higher catalytic activity. Additionally, electrochemical cycling reveals the better stability by TiC@NC(0.2)-800 even after 10,000 cycles (10 mV negative shift in E 1/2) than that of state of art Pt/C catalyst (80 mV negative shift in E 1/2). The presence of N-doped carbon around TiC crystals is responsible for better electrocatalytic activity (due to optimal doping synergy), though the support of TiC makes the electrocatalyst more stable in nature (thanks to strong TiC-NC interactions). Additionally, TiC@NC(0.2)-800 does not show any response towards methanol oxidation reaction, annulling the cross-over effects. Hence, TiC@NC(0.2)-800 could be hopeful substitute for conventional Pt/C electrocatalyst for energy conversion. TiC@NC nanocomposite makes it a significant electrocatalyst for oxygen electroreduction. Image 1 • A simple and facile approach towards synthesis. • Enhanced electroreduction kinetics by titanium carbide and N-doped carbon interface. • Substantial higher E onset of +1.08 vs RHE with J L of 4.8 mA cm−2 under alkaline condition. • Optimized catalyst exhibits much better stability and methanol tolerance property than state-of-the-art Pt/C catalyst. [ABSTRACT FROM AUTHOR]

The development of the fuel cell catalysts with high durability and high activity for oxygen reaction reduction remains a great challenge. Various material designs such as alloys, core@shell structure and shape control provide the promising ways to improve the electrocatalytic performance. Herein, on the basis of both the alloy effect and the nanotube structure effect, we demonstrate a high-performance PtNi alloy catalyst with one-dimensional nanotube structure via a galvanic replacement reaction combined with Kirkendall effect. Meanwhile, the PtNi alloy phase and the tube structure are selectively controlled by tuning the PtNi atomic ratio and the wall thickness of the nanotube, respectively. Subsequently, the understanding of the composition effect and the shape effect on the activity and the durability is systematically investigated. The optimized PtNi nanotube catalyst shows significant improvements on the activity (6.2-fold increase in specific activity compared to the commercial Pt/C) and the durability (only 8.6% loss in mass activity after 10000 cycles), attributing to the alloy effect by introducing Ni to the Pt lattice, the Pt-rich surface and the shape effect of the unique one-dimensional hollow tube structure. Image 1 • PtNi alloy NTs are synthesized with tunable compositions and wall thicknesses. • Composition, size and nanotube effects on the performance are systematically studied. • PtNi-NTs show 1.1 times higher in MA and 6.2 times higher in SA at 0.9 V than Pt/C. • PtNi-NTs achieve an enhanced durability of 8.6% loss in MA after 10 k cycles. [ABSTRACT FROM AUTHOR]

Fuel cells and metal-air batteries have been comprehensively investigated in recent years because of their high energy capacity, good efficiency and environmental friendly nature. Slow kinetics of oxygen reduction reaction (ORR), one of the main processes in fuel cells and metal-air batteries, is improved with platinum catalysts that confine the prevalent utilization of such electrochemical devices with increasing worth for them. However, platinum catalysts after long time usage exhibit weak operations due to the crossover effect and agglomeration. Metal–organic frameworks (MOFs), the porous crystalline materials, consisting of metal centers coordinated to organic ligands, are appropriate catalysts due to their superior properties such as high surface area and carbon content, tunable pore size and diverse metal nodes. In this review, we summarize the recent progress in synthesis and design of MOF-derived ORR electrocatalysts in acidic and alkaline fuel cells. Our focus is on the different methods developed for improving the activity and stability of MOF based ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Development of highly efficient and low-cost electrocatalysts for oxygen reaction is of high importance for the commercialization of fuel cells. In the present study, we synthesized the hybrid of reduced graphene oxide (rGO) supported NiZnO 2 nanoparticles (NPs) as highly efficient non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). The NiZnO 2 NPs composed of ∼8 nm being relatively well distributed and strongly anchored on rGO. Electrochemical test reveals that the NiZnO 2 /rGO exhibits excellent electrocatalytic activity towards ORR, in terms of positive onset potential (0.80 V), high cathode current density (3.49 × 10−4), and low H 2 O 2 yield (about 2%). The mechanism analysis shows that it favors the 4-electron pathway for the reduction of oxygen. Furthermore, the NiZnO 2 /rGO exhibits excellent electrochemical performance in term of durability. Image 1 • NiZnO 2 /rGO is synthesized by a simple hydrothermal method. • NiZnO 2 /rGO shows excellent electrocatalytic activity and durability for ORR. • NiZnO 2 /rGO hybrid catalyzed ORR major happen through 4-electron pathway. [ABSTRACT FROM AUTHOR]

Abstract Small and uniform bimetallic WMoS x nanoparticles well distributed on surface of thin graphene nanosheets (WMoS x -Gr) was prepared and investigated as an effective electrocatalysts for oxygen reduction reaction (ORR) in alkaline electrolyte. This material exhibited highly catalytic activity relative to a commercial Pt/C product. In this context, the material showed a large limit current density, positive onset potential (−0.05 V) as well as half wave potential (−0.13 V). In particularly, the superior durability and methanol tolerance of the as-synthesized material were also pronounced, as compared to Pt/C. The high ORR activity of the WMoS x -Gr material was assumed to the synergistic effect produced from a unique nanostructure of the WMoS x and the high surface area graphene with its excellent conductivity. The obtained results imply that such hybrid material can open a new type of highly efficient non-Pt catalyst for ORR in alkaline environment. Graphical abstract Image 1 Highlights • Uniform WMoS x nanoparticles dispersed graphene is prepared by a facile route. • The hybrid offers high catalytic performance for ORR, comparable to Pt/C. • The synergistic effect from WMoS x and graphene produces enhanced ORR performance. • The hybrid shows much better durability and methanol tolerance than Pt/C. [ABSTRACT FROM AUTHOR]

Abstract Due to the depletion of fossil fuels and severe environmental pollution problems, the urgent demand for clean and sustainable energy sources is constantly emphasized. In recent decades, platinum (Pt)-based fuel cells have achieved tremendous advances as a green energy source, but there is still a need to further improve energy production efficiency in order to realize practical applications. Conventional Pt electrocatalysts are usually insufficient in catalytic activity and the selectivity of electrochemical reactions due to sluggish kinetics and surface poisoning. In contrast, metal alloy nanocatalysts exhibit exceptional electrocatalytic performance on fuel cells, more than pure Pt catalysts, owing to the synergistic effect by systematic modification of the surface geometry and electronic structure of the catalytically active metal component. This review provides overviews and advances in the applications of metal alloy nanohybrid particles enabling the improvement of electrocatalytic efficiency and discusses the challenges and outlooks in the fields of green energy production based on metal alloy nanocatalysts. Graphical abstract Synergistic effects (d -band shift, surface-lattice strain and surface-defects formation) of metal alloy nanocatalysts for the improvement of electrochemical activity. fx1 Highlights • Metal alloy nanocatalysts exhibit exceptional electrocatalytic activity on fuel cell. • Advances of metal alloy particles enhancing electrocatalytic activity are reviewed. • Outlooks in the field of fuel cell based on metal alloy nanocatalysts are discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel low-temperature hydrothermal method is developed to prepare Co-N-rGO. • Co-N-rGO demonstrates higher catalytic activity for ORR than pyrolyzed Co-N-rGO. • Co is coordinated with N which is doped into the rGO structure via covalent bond. • Co and N show synergetic effect in enhancing the ORR activity of rGO. • The active sites responsible for ORR are proposed to be CoN 2 /C and CoN 4 /C species. Abstract Cobalt and nitrogen co-doped reduced graphene oxide (Co-N-rGO) composites are prepared by a facile low-temperature hydrothermal method. Structure characterization reveals that cobalt and nitrogen are co-ordinately attached to the rGO sheets with the formation of covalent C-N and Co-O-C linkages. Cyclic voltammetry and linear sweep voltammetry show that the Co-N-rGO composite possesses higher electrocatalytic activity and four-electron selectivity for oxygen reduction reaction (ORR) as compared to the rGO, Co-rGO and N-rGO. In addition, the Co-N-rGO composite presents excellent stability and durability in alkaline medium comparable to commercial Pt/C. The edge plane CoN 2 /C, CoN 4 /C, and basal plane macrocyclic CoN 4 /C species within the Co-N-rGO structure are proposed to be the active sites performing catalysis in the ORR. The strong covalent linkages between the cobalt/nitrogen and rGO not only enable potent synergy of cobalt, nitrogen and rGO in catalysis, but also ensure structure stability of the composite. Due to the superior ORR activity of Co-N-rGO, high-temperature heat treatment is not able to improve its activity any more. The low-temperature hydrothermal method is anticipated to be used as a low-cost and facile preparation approach for ORR catalysts, and the superb ORR performance of Co-N-rGO endow it with great application potential in fuel cells, metal-air batteries and other ORR-related electrochemical industries. [ABSTRACT FROM AUTHOR]

Abstract Exploiting high efficient non-noble metal catalysts with low-cost and good stability for oxygen reduction reaction (ORR) is vital for fuel cells and metal-air batteries. In this work, we successfully constructed a novel nanosheets-shaped NiCoO 2 hierarchical structure supported on CMK-3 support (i.e. , NiCoO 2 @CMK-3 composite) via a facile hydrothermal method. Electrochemical characterization results reveal that the as-prepared NiCoO 2 @CMK-3 composite exhibits remarkable ORR electrocatalytic activity with a positive peak potential of 0.81 V (vs. RHE), an onset potential of 0.90 V (vs. RHE), a high current density of 4.10 mA cm−2 at 0.4 V, and a nearly four-electron reduction pathway, which are comparable to the state-of-the-art Pt/C catalyst with the same mass. In addition, the NiCoO 2 @CMK-3 composite possesses excellent methanol-tolerance and electrochemical stability, which are better than Pt/C. The outstanding performance confirms the NiCoO 2 @CMK-3 composite as a promising efficient ORR catalyst in fuel cells and metal-air batteries. Graphical abstract A novel NiCoO 2 @CMK-3 composite with nanosheets-shaped hierarchical structure was synthesized via a facile hydrothermal method. The as-prepared NiCoO 2 @CMK-3 composite exhibits comparable ORR electrocatalytic activity and better methanol-tolerance and electrochemical stability to the commercial Pt/C catalyst. The outstanding performance confirms the NiCoO 2 @CMK-3 composite as a promising efficient ORR catalyst in fuel cells and metal-air batteries. Image 1 Highlights • A nanosheets-mesoporous structured NiCoO 2 @CMK-3 composite is successfully synthesized. • The NiCoO 2 @CMK-3 composite exhibits excellent electrocatalytic activity for ORR in alkaline electrolyte. • The NiCoO 2 @CMK-3 composite exhibits excellent methanol-tolerance and electrochemical stability than the Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Abstract The sluggish oxygen reduction reaction (ORR) in cathode is the bottleneck of polymer electrolyte membrane fuel cell. Discovery of ORR catalysts with high activity and low cost is the key solution for the cell development. In this work, we synthesized a novel polypyrrole modified carbon supported FeS (FeS-PPy-BP) through two-step reaction and used it as cathode catalyst in direct borohydride fuel cell (DBFC). The catalyst had an onset ORR potential of 0.89 V (vs. reversible hydrogen electrode (RHE)), little lower than the onset potential of commercial Pt/C. The ORR on the FeS-PPy-BP was mainly through 4-electron process with a low yield of H 2 O 2 (below 5%). The FeS-PPy-BP exhibited a good catalytic stability. The half-wave potential shift of the FeS-PPy-BP after 5000 cycles was 31 mV while that of the Pt/C was 42 mV. The DBFCs using the FeS-PPy-BP as cathode catalyst achieved a maximum power density of 140.5 and 78.8 mW cm−2 at 60 and 30 °C, respectively. The outstanding electrochemical properties and the cell performances strongly support the FeS-PPy-BP as a promising cathode catalyst for DBFC. Graphical abstract Image 1 Highlights • A new FeS-PPy-BP catalyst was synthesized. • FeS-PPy-BP had high ORR activity and good catalytic stability. • DBFC using FeS-PPy-BP as cathode achieved high power density. • FeS-PPy-BP is promising cathode catalyst for DBFC. [ABSTRACT FROM AUTHOR]

Abstract Presently, the practical application of Fe/N/C catalysts as replacements of Pt for oxygen reduction reaction is still limited by insufficient activity. Herein, we demonstrate a novel design for such catalyst. On one hand, the obtained Fe/N/C SiO 2 ZnCl 2 catalyst owns high densities of well-exposed active-sites derived from three-dimensional well-balanced macro-, meso-, and microporous structures constructed by adopting ZnCl 2 salt and SiO 2 microspheres as combined templates. On the other hand, simulation reveals that a high loading of catalyst in cathode catalyst layer would not benefit cell performance and fast oxygen reduction reaction process occurs only inside a limited thickness of catalyst layer. Particularly, the Fe/N/C SiO 2 ZnCl 2 shows a maximal output power density as high as 480 mW cm−2 at an ultra-low loading of 0.5 mg cm−2. This study firstly exhibits that development of catalysts with high-density active sites and construct of ultra-thin catalyst layer are of great significance for improving the performance of fuel cell. Highlights • Fe/N/C SiO 2 ZnCl 2 was synthesized using ZnCl 2 templating and silica templating. • Fe/N/C SiO 2 ZnCl 2 shows superior ORR activity in both alkaline and acidic medium. • The P max of Fe/N/C SiO 2 ZnCl 2 is as high as 480 mW cm−2 at a 0.5 mg cm−2 loading. [ABSTRACT FROM AUTHOR]