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The unique properties of solid acid electrolytes, in particular CsH2PO4, are in many ways ideal for fuel cell operation. However, the technology is constrained by high cathode overpotentials. Here a simplified cathode geometry is employed to obtain the fundamental electrochemical parameters (exchange current density and charge transfer coefficient) describing the oxygen reduction reaction (ORR) at the CsH2PO4‐Pt‐gas interface. The parameters are incorporated into a 1D model of the voltage–current characteristics of realistic SAFC cathodes, which reproduced the measured polarization behavior of such cathodes without recourse to fitting adjustable parameters. Following this validation, the model is utilized to evaluate the impact of changes to cathode properties, microstructure, and operating conditions. Of these, the charge transfer coefficient, measured to have a value of ≈0.6 for ORR on Pt in the SAFC cathode environment, is found to have the greatest impact on power output. Nevertheless, even without material modifications, a combination of microstructural and operational modifications are identified with projected performance metrics meeting Department of Energy targets (0.8 V at 300 mA cm−2, and peak power density of 1 W cm−2), albeit at high Pt loadings. However, the analysis indicates that truly meaningful advances will likely necessitate the discovery of alternative ORR catalysts. [ABSTRACT FROM AUTHOR]

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Coordination environment engineering is developed to synthesize Fe SA /NSC catalysts with the tailored N, S co-coordinated Fe atomic site. [Display omitted] • The Fe-N 3 S active site with the optimized electronic structure is constructed. • S doping promotes the OH* desorption, thus leading to enhanced kinetics process. • The catalyst displays impressive ORR activity in both alkaline and acidic mediums. • The catalyst exhibits excellent performance in Zn-air batteries and fuel cells. Atomically dispersed iron–nitrogen-carbon (FesbndNsbndC) materials have been considered ideal catalysts for the oxygen reduction. Unfortunately, designing and adjusting the electronic structure of single-atom Fe sites to boost the kinetics and activity still faces grand challenges. In this work, the coordination environment engineering is developed to synthesize the Fe SA /NSC catalyst with the tailored N, S co-coordinated Fe atomic site (Fe-N 3 S site). The structural characterizations and theoretical calculations demonstrate that the incorporation of sulfur can optimize the charge distribution of Fe atoms to weaken the adsorption of OH* and facilitate the desorption of OH*, thus leading to enhanced kinetics process and intrinsic activity. As a result, the S-modified Fe SA /NSC exhibits outstanding catalytic activity with the half-wave potentials (E 1/2) of 0.915 V and 0.797 V, as well as good stability, in alkaline and acidic electrolytes, respectively. Impressively, the excellent performance of Fe SA /NSC is further confirmed in Zn-air batteries (ZABs) and fuel cells, with high peak power densities (146 mW cm−2 and 0.259 W cm−2). [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]

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]

The weak interaction between common carbon support and Pt nanoparticles results in low efficiency for the oxygen reduction reaction (ORR) with high overpotentials, which greatly limits the practical application of proton exchange membrane fuel cells. Employing strong metal–support interaction (SMSI) is a promising method for tuning the electronic structure of Pt to boost the ORR, accompanied by rapid improvement in durability. Herein, titanium carbide (TiC) was grown on the surface of carbon black by the sol–gel method coupled with high-temperature treatment (denoted as TiC-C). Based on the SMSI that occurred between TiC and Pt, the obtained Pt/TiC-C catalyst exhibits higher mass ORR activity, which is twice that of the commercial Pt/C-JM under the same conditions. In addition, the Pt/TiC-C exhibits superior durability relative to the Pt/C-JM by preventing the aggregation and dissolution of Pt nanoparticles during the ORR process. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR), an essential reaction in metal–air batteries and fuel cells, still faces many challenges, such as exploiting cost-effective nonprecious metal electrocatalysts and identifying their surface catalytic sites. Here we introduce bulk defects, Frank partial dislocations (FPDs), into metallic cobalt to construct a highly active and stable catalyst and demonstrate an atomic-level insight into its surface terminal catalysis. Through thermally dealloying bimetallic carbide (Co3ZnC), FPDs were in situ generated in the final dealloyed metallic cobalt. Both theoretical calculations and atomic characterizations uncovered that FPD-driven surface terminations create a distinctive type of surface catalytic site that combines concave geometry and compressive strain, and this two-in-one site intensively weakens oxygen binding. When being evaluated for the ORR, the catalyst exhibits onset and half-wave potentials of 1.02 and 0.90 V (versus the reversible hydrogen electrode), respectively, and negligible activity decay after 30,000 cycles. Furthermore, zinc–air batteries and H2–O2/air fuel cells built with this catalyst also achieve remarkable performance, making it a promising alternative to state-of-the-art Pt-based catalysts. Our findings pave the way for the use of bulk defects to upgrade the catalytic properties of nonprecious electrocatalysts. [ABSTRACT FROM AUTHOR]

Due to its exorbitant expense and scarcity on Earth, there is a need to anticipate a cost-effective and widely accessible catalyst that can effectively replace platinum, which is known for its efficiency in fuel cells. In this context, catalysts such as OH, H, and COOH group-functionalized cobalt-doped Graphyne-like boron nitride (referred to as BNyen) are being examined to enhance the mechanism of oxygen reduction reaction (ORR) via direct 4e− reduction. According to findings derived from DFT, it has been observed that reactions predominantly take place above Co metal center rather than edge site of BNyen. Additionally, the thermochemical characteristics point to the fact that these reactions release a significant amount of heat, suggesting their feasibility. By examining reversible potential of products and intermediates on phthalocyanines as well as adsorption energy (E ads), it has been determined that Co-BNyen(OH) serves as a superior catalyst for ORR process. In conclusion, this research affirms that BNyen materials hold significant promise as catalysts for ORR, a crucial process in fuel cell applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Platinum-based catalysts remain the top choice for oxygen reduction reaction (ORR) in fuel cells. However, their activity and durability in the acidic medium are still under improvement. In this work, the Pt nanoclusters anchored the nitrogen-doped carbon nanotubes (Pt-NCNTs) have been synthesized by using a series process of pyrrole coating on the CNTs and subsequent pyrolysis to the chemical immersion reduction of Pt ions. The inner CNTs of Pt-NCNTs function as the nanowires offering a high-speed pathway for electron transport, and the Pt nanoclusters increases the active sites. The theoretical calculation demonstrates that the local structural defects and the uneven charge distribution induced by nitrogen-containing functional groups and porous structure are favorable to capture Pt ions for the nucleation of Pt nanoclusters. Compared with the commercial 40 wt% Pt/C (0.94 and 0.80 V), the Pt-NCNTs-1000 with Pt loading amount of 33.0 wt% owns the more positive onset potential and half-wave potential of 0.97 and 0.81 V in the sulfuric acid medium. Meanwhile, the strong attachment of Pt nanoclusters on the nitrogen-doped porous carbon layer results in a stable interface to effectively prevent the metallic species from migration and agglomeration during the electrode reactions. Therefore, the ORR current of Pt-NCNTs-1000 retained 84.3% of the initial value after 50000 s operation superior to the commercial Pt/C (64.6%). [Display omitted] • N-doped porous carbon layer coated CNT was used as support to enhance Pt deposition. • Micropores and nitrogen groups strongly anchor Pt nanoclusters deposited on NCNTs. • CNTs act as nanowires to promote charges transport of electrode reactions. • Pt-NCNTs has a good ORR activity and durability compared with commercial 40 wt% Pt/C. [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]

The development of new synthetic methods for methanol-tolerant catalysts with improved performance is of fundamental importance for the commercialization of fuel cells. Herein, we reported a facile displacement reaction-assisted synthesis of graphene-supported sub-nanometer Pt/Bi catalysts (Pt/Bi/rGO). Bismuth (0) nanoparticles produced by NH3BH3 reduction can be further dissolved into the ethylene glycol, implying Bi(0) has a strong interaction with the hydroxyl group. That is the key interaction between Bi(0) and the functional group on the rGO to form the ultra-small Bi/rGO catalyst. Furthermore, Pt clusters are obtained by the displacement between Bi(0) and HPtCl4 and are directly anchored to the rGO surface. The as-synthesized Pt/Bi/rGO catalyst exhibits high oxygen reduction mass activity and high tolerance to methanol poisoning. In the presence of 0.5 mol/L CH3OH, the initial potential and activity of ORR were almost unchanged, which demonstrated great potential in the application of direct methanol fuel cells. [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]

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]

Non-precious metal doped carbonaceous materials are currently the most promising alternative towards oxygen reduction reaction (ORR) electrocatalysts in terms of cost, accessibility, efficiency and durability. In this work, a simple one-step pyrolysis process was used for the synthesis of copper doped graphitic carbon nitride (Cu-g-C 3 N 4) as electrocatalyst. The as-synthesized Cu-g-C 3 N 4 material is displaying excellent electrocatalytic response towards ORR in alkaline medium. In comparison to commercial Pt/C catalyst, Cu-g-C 3 N 4 exhibits high methanol tolerance, long term stability, without compromising (4e−) electron transfer pathway process and attaining less than 4% H 2 O 2 formation. The enhanced electrocatalytic behaviour may be ascribed to the formation of active sites strongly coupled into the nitrogen-rich carbon matrix. Such a low-cost, extremely durable and stable electrocatalyst can therefore be regarded as an efficient cathodic material, which can be utilized for several renewable energy conversion technologies such as fuel cell, biofuel cell and metal-air battery. [ABSTRACT FROM AUTHOR]

Single-atom manganese catalysts possess high stability in the oxygen reduction reaction (ORR) due to their lower Fenton reaction activity. Here, we employ N- and S-co-coordination strategy to modulate the microstructural Mn sites towards high-efficiency ORR. The fabricated Mn-N/S-C catalyst with isolated Mn-N 2 S 2 sites demonstrates a positive half-wave potential of 0.91 V for the ORR. The fabricated zinc–air battery with Mn-N/S-C as the cathode affords a maximal power density of 193 mW cm−2 and superior output stability. Moreover, the maximal power density is increased by 1.53 times compared with S-free Mn-N-C catalyst in anion exchange membrane fuel cells (AEMFCs). Both experimental characterizations and theoretical simulations unveil that the main active sites in the Mn-N/S-C should be Mn-N 2 S 2 moiety embedded into the graphene framework (Mn-N 2 S 2 G). Further computational results demonstrate that the S atom doping and asymmetry of structure lead to higher ORR activities of ortho-Mn-N 2 S 2 G than Mn-N 4 G, Mn-N 3 SG, para-Mn-N 2 S 2 G and Mn-NS 3 G. [Display omitted] • N- and S-co-coordination to isolated Mn sites improves the catalytic activity. • The Mn-N/S-C exhibits a positive half-wave potential of 0.91 V for the ORR. • The Mn-N/S-C-based zinc–air battery affords a peak power density of 193 mW cm−2. • The Mn-N/S-C-based AEMFC affords a peak power density of 247 mW cm−2. • Ortho-Mn-N 2 S 2 G shows higher activity than Mn-N 4 G, para-Mn-N 2 S 2 G and Mn-NS 3 G. [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]

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]

Supported ordered intermetallic nanoparticles are of significant interest for catalysis applications owing to their unique surface/near-surface structures and electronic properties. However, the synthesis of small-sized intermetallic catalysts with high mass activity remains a formidable challenge, as high temperatures annealing treatments are generally requisite to achieve ordered intermetallic structures but lead to undesired larger crystallites. Here, we report an industrially relevant impregnation approach for the scalable synthesis of small-sized platinum-based intermetallic nanoparticle catalysts by regulating inter-particle distance on carbon black supports to mitigate metal sintering in high-temperature annealing. We construct a library consisting of 18 binary Pt-based intermetallic nanoparticle catalysts with an average size of < 5 nm. The prepared intermetallic catalyst libraries exhibit outstanding proton-exchange-membrane fuel cells performance, including high mass activities of 1.3–1.8 A mg Pt –1, large peak power densities of 1.2–1.4 W cm–2 in H 2 -air cells, and efficient Pt utilization of ∼0.07 g kW–1 at rated power. [Display omitted] • Intermetallic compounds (IMC) have unique strain/electronic effects in catalysis. • A family of small size Pt-based IMCs was achieved by regulating inter-particle distance. • Small size and ordered IMC structure guarantee outstanding performance in fuel cell. [ABSTRACT FROM AUTHOR]

We synthesized ordered mesoporous Fe/N/C with highly active Fe-N x /C sites denoted as m-FePhen-C as a non-precious metal catalyst (NPMC) for the oxygen reduction reaction in fuel cells. This was the first study that incorporated a catalyst precursor with Fe-N coordination directly in a simple block co-polymer-assisted soft-template method for the synthesis of mesoporous Fe/N/C. The synthesized catalyst (m-FePhen-C) showed a high catalytic performance comparable to that of Pt/C in half-cell tests, and a membrane electrode assembly (MEA) with an m-FePhen-C cathode exhibited 40% higher power density than did an MEA with a commercial Pt/C cathode in single-cell tests, with comparable electrode thicknesses. This result is highly meaningful in that generation of the Fe-N x /C active sites and formation of ordered mesoporous structure were achieved simultaneously in the simple soft-template-assisted process, and in that the advantages of mesoporous structure with appropriate pore size in metal-containing NPMC were elucidated for high-performance MEAs. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is a characteristic reaction which determines the performance of fuel cells which convert a chemical energy into an electrical energy. Aims of this study are to synthesize Au-based nanostars (AuNSs) and determine their preliminary electro-catalytic activities towards ORR by a rotating-disk electrode method in alkaline electrolyte. The images obtained from a scanning electron microscope (SEM) and a transmission electron microscope (TEM) analyses confirm the formation of the star-shaped nanoparticles. Among the investigated nanostar catalysts, an AuNS5 with smaller size and a few branches showed the higher electrocatalytic activity towards ORR than other catalysts with a bigger size. In addition, the electron numbers transferred for all the catalysts are approximately two. The present study results infer that the size of the Au-based nanostars may influence greatly on their catalytic activity. The present study results show that the further improvement is needed for Au-based nanostar catalysts towards the ORR reaction. [ABSTRACT FROM AUTHOR]

Carbon xerogels represent nowadays an outstanding alternative to carbon blacks for the preparation of efficient fuel cell electrocatalysts, due to their easily tunable and well developed mesoporous structure. To further improve both activity and durability of Pt/C catalysts, the introduction of heteroatoms (such as O, N, S, P, B, etc.) in the structure of carbon materials has been proposed. In the present work, highly mesoporous carbon xerogels (CXGs) have been subjected to a sulfurization process with elemental sulfur. The insertion of S into the carbon matrix does not compromise their mesoporous structure. Pt catalysts supported on sulfurized carbon xerogels show enhanced catalytic activity towards both the methanol electro-oxidation and the oxygen electro-reduction reactions, exceeding not only the performance of the catalyst supported on the bare xerogel, but also of the catalyst supported on a commercial carbon black. The sulfurization treatment is also effective in improving the resistance of Pt/CXG catalysts towards corrosion phenomena occurring at the fuel cell cathode. [ABSTRACT FROM AUTHOR]

Three-dimensional nanoporous nitrogen-doped graphene (3D-PNG) has been synthesized through a facial one-step synthesis method without additional silica template. The as-prepared 3D-PNGwas used as an electrocatalyst for the oxygen reduction reaction (ORR), which shows excellent electrochemistry performance, demonstrated by half-cell electrochemical evaluation in 0.1 M KOH including prominent ORR activity, four electron-selectivity and remarkable methanol poisoning stability compared to commercial 20%Pt/C catalyst. The physical and surface properties of 3D-PNG catalyst were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and BET surface area analysis. The experiments show that 3D-PNG catalyst possesses super-large specific surface area reaching 920 m 2 g −1 , which is superior to our most recently reported 3D-PNG synthesized by silica template (670 m 2 g −1 ) and other doped graphene catalysts in literature. When used for constructing a zinc–air battery cathode, such an 3D-PNG catalyst can give a discharge peak power density of 275 mW cm −2 . All the results announce a unique procedure to product high-efficiency graphene-based non-noble metal catalyst materials for electrochemical energy devices including both fuel cells and metal–air batteries. [ABSTRACT FROM AUTHOR]

Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles were nucleated on the surface following procedures found in previous studies. Non-covalent functionalization has been proven to be advantageous because it allows for a better control of particle size and monodispersity, it prevents particle agglomeration since particles are bonded to the surface, and it does not affect the chemical and physical resistance of the support. Synthesized electrocatalysts were characterized by electrochemical half-cell studies, in order to evaluate the Electrochemically Active Surface Area (ECSA), ORR activity, and durability to potential cycling and corrosion resistance. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC) technologies. Downsizing the metal particles to nanoscale introduces unexpected fundamental modifications compared to the corresponding bulk state. To address these fundamental issues, various synthetic routes have been developed in order to provide more versatile carbon-supported low platinum catalysts. Consequently, the approach of using nanocatalysts may overcome the drawbacks encountered in massive materials for energy conversion. This review paper aims at summarizing the recent important advances in carbon-supported metal nanoparticles preparation from colloidal methods (microemulsion, polyol, impregnation, Bromide Anion Exchange...) as cathode material in low temperature FCs. Special attention is devoted to the correlation of the structure of the nanoparticles and their catalytic properties. The influence of the synthesis method on the electrochemical properties of the resulting catalysts is also discussed. Emphasis on analyzing data from theoretical models to address the intrinsic and specific electrocatalytic properties, depending on the synthetic method, is incorporated throughout. The synthesis process-nanomaterials structure-catalytic activity relationships highlighted herein, provide ample new rational, convenient and straightforward strategies and guidelines toward more effective nanomaterials design for energy conversion. [ABSTRACT FROM AUTHOR]

The catalyst of PtCu bimetallic nanoparticles anchored on hierarchical porous N-doped carbon (PtCu/NHPC) is successfully fabricated through a simple pyrolysis synthesis. The high surface area (827 m2 g−1) of N-doped porous carbon (NHPC) can effectively favor the high distribution of PtCu particles on carbon. The high mesopore ratio of NHPC helps to reduce mass transfer resistance. Furthermore, homogeneously distributed nitrogen in carbon can not only uniformly disperse nanoparticles but also optimize catalyst oxygen affinity, significantly improving catalytic efficiency for oxygen reduction reaction. PtCu/NHPC shows excellent electrocatalytic activity with a high half-wave potential (0.915 V vs. RHE) compared with commercial Pt/C (0.864 V) in half-cell test. In the single-cell system, PtCu/NHPC also behaves good performance, and its initial current density is 595 mA cm−2 at 0.85 V. PtCu/NHPC shows better durability (only 6.6% mass activity loss) after 10,000 potential cycles compared to JM Pt/C catalyst (30%). The research provides a simple preparation strategy for improving the oxygen reduction reaction activity and stability of fuel cell platinum-based catalysts. • Hierarchical porous N-doped carbon was prepared through a simple method. • NHPC aids in exposing more active sites and dispersing metal nanoparticles. • The Cu, and N atoms synergistically tune electronic structure of Pt. • Nitrogen doping could enhance the interaction between Pt and NHPC. [ABSTRACT FROM AUTHOR]

The development of non-precious metal catalysts (NPMCs) that are practical for use at the cathode of polymer electrolyte membrane fuel cells (PEMFCs) would provide immense economic advantages, perpetuating the looming widespread commercialisation of these devices. NPMC materials with excellent activity towards the oxygen reduction, coupled with PEMFC performance approaching that of state-of-the-art platinum catalysts brings this technology one step closer to practical application. Currently, the stability of these materials is still limited, and developing NPMC with excellent activity, performance and operational stability is the holy grail of PEMFC catalyst research. Fundamental knowledge available, along with recent progress made in this field of research will be the subject of this review paper. [ABSTRACT FROM AUTHOR]

Macrocyclic compounds such as metallophthalocyanines demonstrated good catalytic activities toward electrochemical reactions. The characteristics of the central cations in metallophthalocyanines significantly influenced their electrocatalytic activities. Addition of conjugated polymers in electrodes improved the electrocatalytic activity by enhancing the electric conductivity. The electrocatalytic activities of macrocyclic compounds could be further improved by heat treatment. The formation of metallic clusters or metal containing organic fragments after pyrolyzing played an important role in improving electrocatalytic activities of macrocyclic compounds. It was considered that macrocyclic compounds might be functioned as a precursor to obtain well-distributed metallic clusters or metal containing organic fragments. [ABSTRACT FROM AUTHOR]

Abstract: A carbon nanotube/perovskite composite material was developed as material for air electrodes in fuel cells or zinc-air batteries. For this purpose, carbon nanotubes were directly grown on the perovskite La0.6Sr0.4CoO3 impregnated with Fe solution which acted as substrate. The synthesis was carried out in a fluidised bed reactor. The carbon source was acetylene. The influence of the temperature on the growth of carbon nanotubes and on the stability of the perovskite was investigated. All samples contained multi-wall carbon nanotubes; however, at a temperature above 675 °C the perovskite was reduced by hydrogen originating from acetylene. The samples with the intact perovskite were further processed to air electrodes to catalyze the oxygen reduction reaction. These electrodes showed an improved performance compared to electrodes made of acetylene black and perovskites. [Copyright &y& Elsevier]

Abstract: Pd nanoparticles supported on WO3/C hybrid material have been developed as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells. The resultant Pd–WO3/C catalyst has an ORR activity comparable to the commercial Pt/C catalyst and a higher activity than the Pd/C catalyst prepared with the same method. Based on the physical and electrochemical characterizations, the improvement in the catalytic performance may be attributed to the small particle sizes and uniform dispersion of Pd on the WO3/C, the strong interaction between Pd and WO3 and the formation of hydrogen tungsten bronze which effectively promote the direct 4-electron pathway of the ORR at Pd. [Copyright &y& Elsevier]

Abstract: A carbon-supported palladium catalyst modified by non-metal phosphorus (PdP/C) has been developed as an oxygen reduction catalyst for direct methanol fuel cells. The PdP/C catalyst was prepared by the sodium hypophosphite reduction method. The as-prepared Pd nanoparticles have a narrow size distribution with an average diameter of 2nm. Energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) results indicate that P enters into the crystal lattice of Pd and forms an alloy. The PdP/C catalyst has an oxygen reduction reaction (ORR) activity comparable to the commercial Pt/C catalyst and a higher activity than the Pd/C catalyst synthesized by the conventional NaBH4 reduction method. Its high catalytic activity can be attributed to its small size, lower relative crystallinity, and the formation of PdP alloy. [Copyright &y& Elsevier]

Abstract: The properties and the oxygen reduction reaction (ORR) characteristics of Pt/C and Corich core–Ptrich shell/C, which were prepared by the thermal decomposition and the chemical reduction methods, annealed in the various conditions were investigated. The alloying degree and grain size of Corich core–Ptrich shell/C analyzed by XRD was increased from 13.10% and 2.45nm to 42.83% and 2.62nm by increasing the time for annealing at 400°C in N2 (annealing condition 1) from 0 to 15h. When the Corich core–Ptrich shell/C was annealed in air at 250°C and then reduced in 6% H2 at 400°C (annealing condition 2), the alloying degree and grain size were obtained to be 47.26% and 3.79nm, respectively. The decrease in the atomic ratio of Co/Pt from 4.77 to 1.34 by annealing Corich core–Ptrich shell/C in condition 1 from 0 to 15h was deduced to be the increase in the Pt loading by the reduction of residual Pt precursor to Pt. The mass and specific activities (MA, SA) of the ORR at 0.9V (versus RHE) on Pt/C annealed in condition 2 were obtained to be 4.11Ag−1 and 6.12μAcm−2, respectively. The MA and SA of Corich core–Ptrich shell/C annealed by condition 2 were 10.07Ag−1 and 11.27μAcm−2. [Copyright &y& Elsevier]

Abstract: We report on the use of dual carbon supports activated charcoal (AC) and Vulcan XC-72R (VC) as catalysts for the fabrication of a gas diffusion electrode. The electrocatalytic properties for the oxygen reduction reaction were evaluated in a sulfuric acid electrolyte using polarization curves and electrochemical impedance spectroscopy. The water uptake and oxygen permeability were also obtained, as were the performances of electrodes in a membrane electrode assembly. A binary support electrode exhibits better performance than the usual single support electrode, with the best performance being obtained when the mass ratio of the two carbons is 50:50. [Copyright &y& Elsevier]

• For the first time, N,S-rGO was used as a support for LDHs in ORR. • CoNiMn-LDH was successfully grown on the surface of N,S-rGO by hydrothermal and coprecipitation method. • 3D nanostructural of CoNiMn-LDH/N,S-rGO composite enhances conductivity, stability and durability as electrocatalyst. [Display omitted] Nowadays, the development of cost-effective and high-performance electrocatalysts towards Oxygen Reduction Reaction (ORR) has attracted great and increasing interest. In spite of the fact that layered double hydroxides (LDHs) have been rarely investigated towards ORR, the considerable issues of low electronic conductivity and self-aggregation of LDHs are not well addressed, which presumably lead to remarkable restrictions on mass transfer. In the present work, nitrogen and sulfur doped reduced graphene oxide (N,S-rGO) with different concentrations are incorporated for the first time into the Cobalt-Magnesium-Nickel LDH (CoMnNi-LDH) structure to improve the ORR efficiency and electrocatalytic activity. Overall, seven electrocatalysts including Graphene Oxide (GO), N,S-rGO, CoMnNi-LDH and its combination with GO and N,S-rGO with different concentrations are fabricated in this work. For assessment of the morphology and structural properties, the synthesized catalysts were characterized by FESEM, TEM, XPS, XRD, EDX, FTIR and Raman techniques. Also, in order to assess the ORR activity and durability, the electrochemical measurements (CV, LSV and chronoamperometric) are carried out for all samples. Based on the obtained results, the best ORR activity is related to the CoMnNi-LDH/15 wt% N,S-rGO electrocatalyst. This result proves that the addition of N,S-rGO to the CoMnNi-LDH with appropriate concentrations can significantly increase the electrocatalytic activity for ORR due to the synergy and strong interaction between them. The onset potential and electron transferred number (n M) of this catalyst are obtained to be −0.04 V vs Ag/AgCl and 3.65, respectively, which it is close to the 4e− pathway for the ORR. Finally, the electrocatalytic activity of prepared electrocatalysts is compared to the commercial 20% Pt/C catalyst. The new reported approach of introducing N,S-rGO support coupled with LDH electrocatalysts provides a novel opportunity to the develop cost-effective and durable electrocatalyst for fuel cell technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Method for synthesizing metal-free electrocatalyst with highly ordered nanochannels. • Thermal treatment in NH 3 atmosphere for activation of catalyst surface toward oxygen reduction. • Improved performance after stability test owing to ordered nanostructure with activated surface. • Verification of variations in N-containing species during oxygen reduction reaction. Lowering the cost of electrocatalysts for the oxygen reduction reaction (ORR) is indispensable for the wider commercialization of fuel cells. Therefore, the development of non-Pt, especially metal-free, carbon-based electrocatalysts, has been encouraged as an alternative to Pt. Here, we report active N-doped nanocarbon electrocatalysts in ORR activated by thermal treatment of pristine carbon precursors with highly aligned mesopore channels under an NH 3 atmosphere. This NH 3 -activation process adopts N-containing carbon sites, leading to enhanced ORR performance in an alkaline electrolyte with negligible formation of peroxide species. The stability of the activated carbon electrocatalysts was confirmed by performing 40,000 rounds of potential cycles in the accelerated stress test (AST). The variations in the voltammograms during AST were analyzed using X-ray photoelectron spectroscopy. The correlation between electrochemical behavior and the N 1 s spectrum corroborates the contribution of N-related sites toward voltammetric responses in ORR. [ABSTRACT FROM AUTHOR]

Development of low-cost and high-efficient oxygen reduction reaction (ORR) catalyst is a crucial challenge in fuel cell technology. Herein, we proposed a simple and scalable strategy to fabricate an interconnected 3D Fe 3 O 4 /rGO composite, in which Fe 3 O 4 nanoparticles mechanically anchor in reduced graphene oxide (rGO). Benefiting from its 3D layered structure with loose skeleton and rich porosity, and strong synergetic coupling between Fe 3 O 4 nanoparticles and rGO, the prepared composite, Fe 3 O 4 /rGO, provides better catalytic performance for ORR compared with commercial Pt/C catalyst, featuring high limiting current density (4.6 mA cm−2) close to that of Pt/C (4.7 mA cm−2), low H 2 O 2 yield (1%–6%), high electron transfer number (∼4), and outstanding long-term durability and methanol resistance in alkaline electrolytes. These encouraging results manifest that the Fe 3 O 4 /rGO composite holds great promise as a low-cost and high-performance alternative catalyst for ORR. • Simple and effective method to prepare 3D structured Fe 3 O 4 /rGO as ORR catalyst. • Fe 3 O 4 /rGO has a 3D layered structure with loose skeleton and rich porosity. • Fe 3 O 4 with an average particle size of about 20 nm uniformly anchored on graphene. • Fe 3 O 4 /rGO shows similar catalytic activity and better stability compared with Pt/C. [ABSTRACT FROM AUTHOR]

This study reports on protonic ceramic fuel cells (PCFCs) that exhibit enhanced performance after the addition of palladium (Pd) interlayers at the cathode–electrode interface. The Pd interlayer is deposited by sputtering on the BaZr 0.2 Ce 0.6 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) electrolyte surface, followed by the inkjet printing of PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) and sintering. The proposed method successfully has produced a Pd layer that was well integrated between the BZCYYb and PBSCF layers, with no undesired reactions or phase formation. The Pd layer is diffused along the inner surface of the porous PBSCF cathode with the desired gradient composition. In our experiment, the fuel cell power is enhanced by up to 60% compared to the untreated PCFCs. In the former, the peak power density of the optimal cell is 420 mW cm−2, while that of the untreated sample is 260 mW cm−2 at 500 °C. The long-term stability of the Pd interlayer is confirmed during cell operation. The impedance analysis has revealed that the presence of the Pd significantly enhances the current collection and reduces the polarization impedance at the cathode–electrolyte interface, especially at low temperatures. These results indicate that the proposed method is promising for the fabrication of high-performance and robust PCFCs. • Palladium-rich layer is inserted between electrolyte and cathode of PCFC using DC sputter. • Co-sintering of palladium and cathode formed gradient palladium-rich layer. • Palladium-rich layer enhanced the reaction at the cathode of PCFC. • Fuel cell performance is highly affected by the amount of palladium. [ABSTRACT FROM AUTHOR]

Developing cost-effective and high active catalysts for the oxygen reduction reaction (ORR) is vital for the application of fuel cells. In this work, nitrogen-doped porous carbon nanosheets(N-PC) derived from biomass waste soybean residue were prepared by a facile combining method of solid state grinding and pyrolysing, using g-C 3 N 4 as both nitrogen source and sacrificial template. The benefit of this facile process is that neither a designated template nor a chemical activating agent is required. The influence of g-C 3 N 4 level on the structure and ORR behavior of the resulting N-PC was systematically investigated by means of spectroscopy (XPS), surface area analysis (BET), electron microscopy (TEM, SEM) et al., and electrochemical experiments. The optimized sample possesses appropriate defect structure, high BET surface area and pore volume (483 ​m2 ​g−1 and 1.57 ​cm3 ​g−1), and high N content (6.04 ​at.%), and exhibits decent activity and methanol tolerance in ORR process. Its superior stability versus the commercial Pt/C is also evidenced by almost 50% higher in chronoamperometric current response after 3600 ​s testing duration. This work supplies a simple and economical route to synthesize superior electrocatalyst for ORR on the basis of biomass waste. N doped porous carbon materials (N-PC) were prepared by a facile strategy using biomass waste soybean residue as carbon source.The optimized N-PC presents superior catalytic activity and stability in ORR. Image 1 [ABSTRACT FROM AUTHOR]

• Facile synthesis of cobalt oxides incorporated covalent organic frameworks. • High catalytic activity, poison tolerance and good durability of Co/N-C-COPs. • Co/N-C-COPs prepared at 800 °C exhibited the best ORR catalytic activity. • Power output of Co/N-C-COPs cathode is similar to Pt/C cathode in MFC and DFFC. Synthesizing high efficient oxygen reduction reaction catalyst is crucial for electrochemical technologies such as fuel cells. Herein, we proposed a covalent organic polymers derived carbon with cobalt oxides incorporation (Co/N-C-COPs) as ORR electrocatalysts for fuel cells. The Co/N-C-COPs was demonstrated to possess sufficient active sites and uniformly dispersed cobalt and nitrogen elements. The as-prepared Co/N-C-COPs at 800 °C showed the best ORR catalytic activity with a half-wave potential (−0.16 V vs. Ag/AgCl) and limiting current density (3.99 mA cm−2) similar to that of Pt/C (−0.15 V vs. Ag/AgCl and 4.05 mA cm−2) in alkaline media. When using the Co/N-C-COPs as cathode electrocatalyst, two types of home-made fuel cells (microbial fuel cell and direct formate fuel cell) delivered a comparable or even higher power output than that using Pt/C, due to its intriguing features including high catalytic activity, high poison tolerance and good durability. These results suggested that the as-proposed Co/N-C-COPs catalyst probably provide an alternative avenue for developing the cathode electrocatalysts for fuel cell applications. [ABSTRACT FROM AUTHOR]

• An overview of the state-of-the-art in oxygen reduction reaction is presented. • In-depth discussion of carbon dots and their practical applications in fuel cell. • An analysis of recent progress in carbon nanotubes applied on a fuel cell. Proton exchange membrane fuel cell (PEMFC) is receiving strong attention in sustainable energy conversion and storage systems. Its high efficiency, low emission, and environmental friendliness enable hydrogen fuel cell electric vehicle (FCEV) for day to day transportation. High costs, limited durability and inefficient oxygen reduction reaction (ORR) have been identified as key challenges for the widespread commercial success of fuel cell transportation vehicles. ORR is constrained by slow kinetics of cathode catalyst and must be improved by suitable nanoengineering of low-cost electrocatalysts. Replacing platinum group metals with carbon-based non-precious metal is a promising solution. Recently, advances in zero-dimensional carbon dots are showing promise for challenging energy-oriented issues. In addition, the one-dimensional carbon nanotubes are also found suitable for efficient ORR. However, carbon-based electrocatalyst showing improved performance in electrochemical measurements are not up to the expectation in the practical application of FCEV. This review highlights the advancement and future opportunities for improving performance of ORR using carbon dots and carbon nanotubes nanostructures. We discussed the application of carbon dots and carbon nanotubes in the fuel cell. Their corresponding electrochemical performance was presented. Followed by, practical application of carbon nanotubes in the real operating condition of PEMFC was discussed. Finally, the current status and future target of FCEV were comprehensively addressed. [ABSTRACT FROM AUTHOR]

Stable hybrid silica decorated carbon composite is realized for improving oxygen reduction kinetics, performance and stability of polymer electrolyte fuel cell. Synthesis of platinum on an optimum level of silica decorated into carbon via single-step polyol method with minimum loading of platinum (0.15 mg cm−2) shows superior power density of 1.45 W cm−2 in relation to platinum on carbon. The optimum composition of silica decorated carbon preserves 70% of the electrochemical active surface area of platinum even after 6000 cycles from 1 to 1.5 V. The water retention ability for silica is responsible for maintaining the humidity within the triple phase boundary of the membrane electrode assembly, which in turn increases the fuel cell performance and stability even up to 100 h under low humidity. Besides, air-cooled prototype 15 cell stack is assembled comprising the above electrocatalyst which exhibits the power output of 100 W at 10 V under 40% relative humidity. Image 1 • Silica-decorated carbon-Pt electrocatalyst is synthesized. • Pt/CS 3 electrocatalyst show higher oxygen reduction activity. • Pt/CS 3 electrocatalyst show higher PEFC performance under low humidity. • Pt/CS 3 electrocatalyst shows enhanced stability when compared with Pt/C. • 15 cell stack comprising Pt/CS 3 catalyst is also explored under low humidity. [ABSTRACT FROM AUTHOR]

Large quantities of marine algae are annually produced, and have been disposed or burned as solid waste. In this work, porous carbons were prepared from three kinds of marine algae (Enteromorpha, Laminaria, and Chlorella) by a two-step activation process. The as-prepared carbon materials were doped with cobalt (Co) and applied as catalysts for oxygen reduction reaction (ORR). Our results demonstrated that Co-doped porous carbon prepared from Enteromorpha sp. (denoted by Co-PKEC) displayed excellent catalytic performance for ORR. Co-PKEC obtained a half-wave potential of 0.810 V (vs. RHE) and a maximum current density of 4.41 mA/cm2, which was comparable to the commercial 10% Pt/C catalyst (E1/2 = 0.815 V, Jd = 4.40 mA/cm2). In addition, Co-PKEC had excellent long-term stability and methanol resistance. The catalytic ability of Co-PKEC was evaluated in a one-chamber glucose fuel cell. The maximum power density of the fuel cell equipped with the Co-PKEC cathode was 33.53 W/m2 under ambient conditions, which was higher than that of the fuel cell with a 10% Pt/C cathode. This study not only demonstrated an easy-to-implement approach to prepare robust electrochemical catalyst from marine algal biomass, but also provided an innovative strategy for simultaneous waste remediation and value-added material production. [ABSTRACT FROM AUTHOR]