Improved Oxygen Reduction Reaction Activity Research Articles

Pt-based Rare Earth Alloy as Efficient and Robust Electrocatalyst for High-temperature Proton Exchange Membrane Fuel Cells.

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are crucial in future energy system. However, the activity and stability of the electrocatalysts are severely restricted by high temperature and phosphoric acid poisoning. Herein, PtCe alloy as oxygen reduction reaction (ORR) electrocatalyst for HT-PEMFCs exhibits fantastic performance. Ce can increase the electronic density of Pt weakening phosphoric acid poisoning and improving ORR activity. The optimized electronic structure can also reduce the dipole effect between Pt and O, which suppresses the irreversible oxidation of Pt. Additionally, the dramatically negative heat of formation in PtCe catalyst brings high kinetic barrier of metal diffusion and dissolution. With this electrocatalyst, the HT-PEMFCs show a preeminent peak power of 605 mW cm-2 with 0.3 mgPt cm-2. After 30000 cycles of accelerated stability test, the peak power density only decreases by 31.6 %, achieving the goal of Department of Energy in 2020 (＜40 % loss).

Tuning Carbon Defect in Copper Single-Atom Catalysts for Efficient Oxygen Reduction.

Defect chemistry in carbon matrix shows great potential for promoting the oxygen reduction reaction (ORR) of metal single-atom catalysts. Herein, a modified pyrolysis strategy is proposed to tune carbon defects in copper single-atom catalysts (Cu-SACs) to fully understand their positive effect on the ORR activity. The optimized Cu-SACs with controllable carbon defect degree and enhanced active specific surface area can exhibit improved ORR activity with a half-wave potential of 0.897 VRHE , ultrahigh limiting current density of 6.5mA cm-2 , and superior turnover frequency of 2.23 e site-1 s-1 . The assembled Zn-air batteries based on Cu-SACs can also show well-retained reversibility and voltage platform over 1100h charge/discharge period. Density functional theory calculations reveal that suitable carbon defects can redistribute charge density of Cu-N4 active sites to weaken the O-O bond in adsorbed OOH* intermediate and thus reduce its dissociation energy. This discovery offers a universal strategy for fabricating superior single-atom catalysts with high-efficiency active sites toward energy-directed applications.

Synergistic Catalytic Effects of CeCuO3 @ Vulcan Carbon Composites on the Oxygen Reduction Reaction

AbstractThe reduction of molecular oxygen is considered to be a key reaction for electrochemical energy conversion in direct methanol fuel cells (DMFCs). The slow kinetics of oxygen reduction reaction along with the high cost of Pt catalyst hampers the application of fuel cells. In this study, we have reported for the first time oxygen reduction reaction (ORR) activity on rare earth cerium containing perovskite oxides composite with vulcan carbon (VC) in alkaline media. The study has demonstrated the synergistic role of vulcan carbon in cerium perovskite nanomaterials‐VC composite for improving ORR activity. The 60 % CeCuO3‐VC perovskite oxide composite with surface areas of 180 m2/g showed better oxygen reduction capability as compared to that of bare cerium perovskite. On optimization, among all the prepared catalysts 60 % CeCuO3‐VC showed the highest ORR activity with low onset potential and high current density. Further, the optimized 60 % CeCuO3‐VC followed the 4e− pathway with 95 % methanol tolerance properties and high stability i.e 76 %. This study on cerium‐based perovskite with vulcan carbon will provide an opportunity for the study of rare earth cerium perovskite electrocatalysts for electrochemical energy conversion.

Nanostructure Engineering and Electronic Modulation of a PtNi Alloy Catalyst for Enhanced Oxygen Reduction Electrocatalysis in Zinc-Air Batteries.

PtNi nanoalloys have demonstrated electrocatalysis superior to that of benchmark Pt/C catalysts for the oxygen reduction reaction (ORR), yet the underlying mechanisms remain underexplored. Herein, a PtNi/NC catalyst comprising PtNi nanoparticles (∼5.2 nm in size) dispersed on N-doped carbon frameworks was prepared using a simple pyrolysis strategy. Benefiting from the individual components and a hierarchical structure, the PtNi/NC catalyst exhibited outstanding ORR activity and stability (E1/2 = 0.82 V vs RHE and 8 mV negative shift after 20000 cycles), outperforming a commercial 20 wt % Pt/C catalyst (E1/2 = 0.81 V and 32 mV negative shift). A prototype zinc-air battery constructed using PtNi/NC as the air electrode catalyst achieved highly enhanced electrochemical performance, outperforming a battery constructed using Pt/C as the ORR catalyst. Density functional theory calculations revealed that the improved ORR activity of the PtNi nanoalloys originated from charge redistribution with a suitable metal d-band center to promote the formation of the ORR intermediates.

The synthesis of iron-nitrogen sites embedded in electrospun carbon nanofibers with an excellent oxygen reduction reaction activity in alkaline/acidic media

Metal-nitrogen carbon catalysts have received great attention in the field of gas-evolving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion paths. A solution of porphyrin iron, g-C3N4 and polyacrylonitrile in N,N-dimethylformamide was sonicated and electrospun into doped polyacrylonitrile nanofibers (NFs), and the NFs were then stabilized and carbonized at 900 °C to prepare Fe-N/CNF catalyst for oxygen reduction reaction (ORR). It was found that the addition of g-C3N4 to the electrospinning precursor led to the formation of abundant Fe-N species in Fe3+ and Fe2+ valence states, while Fe3C nanoparticles were formed without adding g-C3N4. Compared to Fe3C/CNF prepared without g-C3N4, the Fe-N/CNF catalyst presents an 4e− improved oxygen reduction reaction activity in both alkaline and acidic media. Furthermore, as a cathode in Zn-air batteries, the Fe-N/CNF catalyst exhibits high performance with an open-circuit voltage of 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh g-1. This work suggests a way to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.

Atomistic understanding of Pt-based medium entropy alloys for oxygen reduction electrocatalysis based on first principles

Platinum (Pt)-based multicomponent alloys have been widely regarded as the best catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Herein, a set of Pt-based medium entropy alloys with precisely controllable composition and structure have been designed theoretically. The obtained medium entropy alloys like PtCuSn or PtCuW tend to form an atomistic thick Pt-skin structure with W or Sn atomic segregation at the subsurface. Based on oxygen reduction kinetic current calculations, the PtCuSn exhibits an onset potential of 1.09 V and half-wave potential of 0.86 V and also displays increased vacancy energy, revealing remarkably enhanced intrinsic activity and structural stability, compared with the other tested Pt-based catalysts. The improved ORR activity can be attributed to unique electronic structure, compressive microgeometry, and low work function. This work can shed a light on the design of novel medium-, high-entropy nanoalloys as next-generation catalysts for PEMFCs.

Tuning oxygen reduction reaction activity via structure orientation and surface arrangement: A study on ordered PtCo/C catalysts

A facile and general strategy for the preparation of highly dispersed PtCo/C catalysts with a Pt-enriched surface is reported. The thermal treatment of the PtCo/C catalyst changes the structure orientation from disordered to ordered phase. Ordered PtCo/C intermetallic catalyst exhibits significantly enhanced electrocatalytic activity and durability toward oxygen reduction reaction (ORR) compared with its disordered counterpart and commercially available PtCo/C, with a mass activity and specific activity of 0.68 A mg Pt−1@0.90 V and 1.15 mA cm−2, respectively. In addition, the mass activity only decreased by 25.1% after 30,000 potential cycles from 0.60 to 1.00 V at a scan rate of 100 mV s−1. Therefore, the improved ORR activity and stability can be ascribed to the atomic ordered surface arrangement and reasonable surface compress strain originated from Pt-enriched surface.

A/B-site co-doping enabled fast oxygen reduction reaction and promoted CO2 tolerance of perovskite cathode for solid oxide fuel cells

The significant challenges facing the development of the cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) are the poor oxygen reduction reaction (ORR) activity as well as the CO2 poisoning issues. Herein, an La/Nb co-doped perovskite Ba0.9La0.1Co0.7Fe0.2Nb0.1O3-δ (BLCFN) has been developed as a promising cathode for IT-SOFCs. The polarization resistance of BLCFN cathode is 0.073 Ω cm2 at 700 °C air. This remarkable improved ORR activity can be attributed to the increased oxygen vacancies caused by the introduction of La3+ and Nb5+ ions. Furthermore, the collaboration introduction of La3+ and Nb5+ ions greatly reduce the alkalinity of the BLCFN electrode, bringing excellent CO2-tolerance for BLCFN cathode. No carbonate is yielded on the surface of the BLCFN cathode. The improvement on CO2-tolerance for these cathodes is largely attributed to the introduction of Nb5+ ions, which have higher acidity and more powerful M − O bond, and the introduction of La3+ can improve the ORR activity of the material on this basis. The co-doping of La/Nb elements furtherly stabilizes the lattice structure. Overall, the high ORR activity and CO2-tolerance of the cathode manifest a bright application prospect for BLCFN cathode in SOFCs and other membrane reactors.

Enhanced Activity of Oxygen Reduction Reaction on Pr6O11-Assisted PtPr Alloy Electrocatalysts.

Pt-based alloy catalysts for oxygen reduction reaction (ORR) with outstanding performance have been well-studied in recent years. Among these, Pt-lanthanide alloy catalysts have been developed with quite a competitive ORR activity. However, to promote practical applications of a proton-exchange membrane fuel cell (PEMFC), catalysts with superior activity are still being explored. Herein, we present the Pr6O11-assisted Pt-Pr catalyst exhibiting further improved ORR activity than the state-of-the-art Pt/C. A simple annealing treatment is applied after the synthesis of the Pt-Pr alloy, obtaining Pr6O11 nanoparticles attached to the surface of the Pt-Pr alloy to form a Pt-Pr/Pr6O11 composite catalyst. Experimental and theoretical studies reveal that the electronic state of Pt in the Pt-Pr/Pr6O11 system is modified. It was found that the strong oxophilicity of Pr adjusts the active site of Pt and promotes the adsorption and dissociation of O2. The preeminent intrinsic ORR activity on the Pt-Pr/Pr6O11 catalyst reaches the promoted specific activity (2.01 mA cm-2) and mass activity (1.3 A mgPt-1), which were 5.91- and 5.90-fold higher than those obtained by the state-of-the-art Pt/C catalyst (0.34 mA cm-2 and 0.22 A mgPt-1). This study provides us with an idea that the ORR performance of Pt-based alloy could be enhanced with the assistance of the metal oxide phase.

Nitrogen-doped carbon nanotubes filled with Fe3C nanowires for efficient electrocatalytic oxygen reduction

It is of great significance to develop the highly active, durable and inexpensive oxygen reduction reaction (ORR) electrocatalysts for fuel cells and metal-air batteries. Nitrogen-doped carbon nanotube (NCNTs) was considered to be one of the most significant non-noble metal ORR electrocatalysts, but its catalytic activity has some shortcomings due to its unfavorable ORR intermediates adsorption characteristics. Herein, we report a new kind of nitrogen-doped carbon nanotubes, which have filled with Fe3C nanowires (NCNTs@Fe3C NWs), working as a stable and effective ORR catalyst. The half-wave potential of the obtained catalyst in a 0.1 M KOH solution is 0.88 V, which is significantly higher than the pristine NCNTs (0.79 V) and the commercial Pt/C (0.85 V). Compared with NCNTs, the improvement in ORR activity of NCNTs@Fe3C NWs can be attributed to the strain effect on the outermost carbon layer due to the high filling of Fe3C NWs. Most importantly, NCNTs@Fe3C NWs shows higher durability and better methanol tolerance than the commercial Pt/C catalyst. Density functional theory (DFT) calculation shows that the tensile strain can optimize the binding energy of ORR intermediates to a certain extent. This work provides new research ideas for the rational design of high-efficiency carbon-based ORR electrocatalysts through the direction of strain engineering.

Synthesis of Mesoporous Fe/N/C Electrocatalyst for Improved Oxygen Reduction Reaction Activity Through CO2‐Assisted Pyrolysis

AbstractFe/Nx/C electrocatalysts have appeared as one of the promising non‐platinum group metal (non‐PGM) electrocatalysts for oxygen reduction reaction (ORR) in energy conversion devices. These non‐PGM electrocatalysts Fe/N/C need structural tuning of pores to improve the surface area for high‐performance ORR in proton exchange membrane fuel cells. In this report, the specific surface area of poly‐melamine‐formaldehyde (PMF)‐based Fe/N/C electrocatalysts was enhanced without using a template through simple CO2‐assisted pyrolysis. The highly porous electrocatalyst exhibited an onion‐like graphitic structure and an efficient catalytic activity for ORR, comparable to Pt/C electrocatalyst. At 0.95 VRHE, the mass activity of the PMF‐based PMF−Fe/N/C‐CO2/Ar electrocatalyst was 63 % that of a commercial Pt/C electrocatalyst. Moreover, the devised fabrication process for the PMF−Fe/N/C electrocatalysts with a high specific surface area can be readily scaled up.

Improving Electroactivity of N-Doped Graphene Derivatives with Electrical Induction Heating.

Graphene derivatives doped with nitrogen have already been identified as active non-noble metal materials for oxygen reduction reaction (ORR) in PEM and alkaline fuel cells. However, an efficient and scalable method to prepare active, stable, and high-surface-area non-noble metal catalysts remains a challenge. Therefore, an efficient, potentially scalable strategy to improve the specific surface area of N-doped graphene derivatives needs to be developed. Here, we report a novel, rapid, and scalable electrical induction heating method for the preparation of N-doped heat-treated graphene oxide derivatives (N-htGOD) with a high specific surface area. The application of the induction heating method has been shown to shorten the reaction time and improve the energy efficiency of the process. The materials synthesized by induction heating exhibited very high specific surface area and showed improved ORR activity compared to the conventional synthesis method. Moreover, we demonstrated that the temperature program of induction heating could fine-tune the concentration of nitrogen functionalities. In particular, the graphitic-N configuration increases with increasing final temperature, in parallel with the increasing ORR activity. The presented results will contribute to the understanding and development of nonmetal N-htGOD for energy storage and conversion applications.

Improved oxygen reduction reaction activity by in-situ synthesizing Sr3Fe1.8Nb0.2O7-δ coating on SrFe0.9Nb0.1O3-δ cathode via the microwave water bath heating method

The sluggish oxygen reduction kinetics remains to be the main obstacle to the development of low temperature proton ceramic fuel cells which limits its commercial application. This phenomenon has driven the exploration of the oxide electrode materials which both possess high oxygen reduction reaction activity and heterogeneous structure. In this work, mixed ionic and electronic conductor SrFe0.9Nb0.1O3-δ (SFN113) is partially transformed into the triple-phase conductor Sr3Fe1.8Nb0.2O7-δ (SFN327) by in-situ reaction with uniformly coated SrO layer using a microwave water bath heating method. The introduction of the second phase SFN327 significantly improves the oxygen surface exchange kinetics of SFN113 investigated by the electrical conductivity relaxation method. The present work not only remarkably improves the electrocatalytic reduction activity of SFN113 by the introduction of the second phase SFN327 and the construction of the heterogeneous interface, but also provides a valuable route for the further optimization of the exiting electrode materials.

Atomically Dispersed Hollow Spherical Bimetallic(Co, Fe) Electrocatalysts Using Spray Pyrolysis with Improved Stability for Oxygen Reduction Reaction in Acidic Condition

Pt and Pt-based alloys have been proven to be the most efficient catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, their susceptibility to CO deactivation and high cost as well as the limited reserves of Pt hinder their practical application. M-N-C catalysts for ORR from low-cost and earth abundant metal elements have exhibited a great promise to replace current platinum-based catalysts for PEMFCs. But insufficient stability is the major hurdle to prohibit their practical applications. In this study, we designed and synthesized bimetallic electrocatalysts which have enhanced stability in acidic condition with improved ORR activity by making metal interactions. Bimetallic (Co, Fe) oxides were prepared first by spray pyrolysis. Spray pyrolysis has advantages of component dispersibility and making hollow sphere that is ideal structure for mass transport without template. The product electrocatalysts showed high surface area and catalytic activity with reduced mass transport resistance. The synthesized bimetallic catalysts were analyzed by BET, XAFS, HR-STEM and electrochemical analysis system.

Optimization of Synthesis Variables Towards Improved Activity and Stability of Fe-N-C PGM-Free Catalysts

Materials in the Fe-N-C family are the most promising platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs).1-3 Although significant progress has been made in recent years in improving both the ORR activity and durability of the Fe-N-C catalysts, further improvements are needed, especially in long-term performance durability in hydrogen-air PEFCs, to enable their use in applications such as propulsion power for light-duty vehicles.3 The most active ORR catalysts in the Fe-N-C family were synthesized by heat treating iron salts or other iron-containing compounds with zinc-based zeolitic imidazolate frameworks (ZIFs) and/or phenanthroline (as carbon and nitrogen sources), or by heat treating iron-substituted ZIFs. For this family of PGM-free materials, it has been shown that many synthesis variables, such as the metal and carbon-nitrogen macrocycle content, the heat treatment temperature, atmosphere, and temperature profile all affect the activity and durability of the resulting catalysts.4-7 Optimization of these variables and testing the resulting catalyst properties is not a trivial task, and only a limited portion of the composite composition and temperature space has been explored for this family of catalysts.To accelerate optimization of the synthesis variables to obtain improved ORR activity and stability for the Fe-N-C catalysts, high-throughput synthesis and characterization methods were developed and utilized. An automation platform, a multi-port ball-mill, and parallel fixed bed reactors in Argonne’s High-throughput Research Laboratory were used to rapidly synthesize the PGM-free catalysts with systematically-varied synthesis conditions. A multi-channel flow double electrode (m-CFDE) cell and other cells were designed and constructed for the simultaneous testing the ORR activity and stability of the multiple catalysts synthesized. The ORR activity and stability of the catalysts were correlated with their Fe speciation, as determined using Fe K-edge X-ray absorption spectroscopy (XAFS), electrochemically-determined surface areas, and other variables, which is beneficial for the further improved catalyst activity and stability.References B. Pivovar, Nature Catalysis, 2 (2019) 562.S. Thompson and D. Papageorgopoulos, Nature Catalysis, 2 (2019) 558.L. Osmieri, J. Park, D.A. Cullen, P. Zelenay, D.J. Myers, and K.C. Neyerlin, Curr. Opin. Electrochem., 25 (2021) 100627.X. Wang, H. Zhang, H. Lin, S. Gupta, C. Wang, Z. Tao, H. Fu, T. Wang, J. Zheng, G. Wu, and X. Li, Nano Energy, 25 (2016) 110.H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, and G. Wu, J. Am. Chem. Soc., 139 (2017) 14143-14149.E. Proietti, F. Jaouen, M. Lefevre, N. Larouche, J. Tian, J. Herranz, and J.-P. Dodelet, Nature Comm. 2 (2011) 1.A. Zitolo, V. Goellner, V. Armel, M.-T. Sougrati, T. Mineva, L. Stievano, E. Fonda, and F. Jaouen, Nature Materials, 14 (2015) 937. This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat). This work utilized the resources of the Advanced Photon Source, a U.S. DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office and was authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.

Deciphering the Role of Substitution in Transition-Metal Phosphorous Trisulfide (100) Surface: A Highly Efficient and Durable Pt-free ORR Electrocatalyst.

The rational design and development of earth-abundant, cost-effective, environmentally benign, and highly robust oxygen reduction reaction (ORR) electrocatalysts can circumvent the obstacles associated with the large-scale commercialization of fuel cells. Here, using first-principles-based density functional theory (DFT), we have computationally screened the potential and feasibility of transition-metal phosphorous trisulfides (TMPS3 ) (100) surfaces as efficient ORR electrocatalyst in acidic fuel cell application. MnPS3 (100) surface emerges to be the best among TMPS3 surfaces with optimal O2 activation resulting in very low overpotential. The study reveals that ORR occurs on the MnPS3 surface via 4e reduction associative pathway where the kinetically rate-determining step (RDS) is the formation of O*+H2 O with an activation barrier of 0.66 eV. Additionally, high CO tolerance and easy desorption of H2 O make MnPS3 a robust catalyst. Substitution in half of the Mn sites of MnPS3 (100) surface with Co considerably enhances the ORR activity. Mn0.5 Co0.5 PS3 (100) surface exhibits an ultralow overpotential of 0.39 V vs RHE switching ORR pathway from associative to dissociative. Spontaneous dissociation of H2 O2 on Mn0.5 Co0.5 PS3 proves 4e reduction pathway excluding 2e one. Electronic structure analysis reveals that pristine MnPS3 (100) surface is a narrow band gap semiconductor which upon Co substitution transforms into a conducting metallic surface enhancing ORR activity. Besides, Mn0.5 Co0.5 PS3 (100) surface obtains the apex of the volcano plot due to its optimal position of the d-band center which further justifies the improved ORR activity. With Pt-like onset potential, facile H2 O desorption ability, and robust dynamic and thermal stability, this CO tolerant Mn0.5 Co0.5 PS3 catalyst can be a potential alternative to Pt with encouraging practical viability.

Engineering asymmetric Fe coordination centers with hydroxyl adsorption for efficient and durable oxygen reduction catalysis

Single-atom Fe catalysts are a promising substitute to Pt catalysts for oxygen reduction reaction (ORR). Adjusting metal energy level through direct atomic interface regulation can effectively improve catalytic performance but still in its infancy. Herein, highly active nitrogen and sulfur dual-coordinated asymmetric Fe center anchored in carbon nanoparticles were developed. Spontaneously absorbed OH ligand is steadily anchored in asymmetric atomic interface, constructing new FeN3S-OH moiety. Theoretical calculations reveal that the incorporated S atom combined with OH ligand as energy level modifier effectively activate Fe center by electronic modulation and d-band center shift, rendering improved ORR activity of FeNSC-2Fe with E1/2 of 0.913 V in alkaline, 0.806 V in acidic and 0.711 V in neutral media. The FeNSC-2Fe-based device displays high power density of 306 mW cm−2 in Zn-air battery and 2485 mW m−2 in microbial fuel cell. This work provides a new perspective for the controllable synthesis and performance optimization for electrocatalysts.

Atomic Structure Modification of Fe‒N‒C Catalysts via Morphology Engineering of Graphene for Enhanced Conversion Kinetics of Lithium–Sulfur Batteries (Adv. Funct. Mater. 19/2022)

Multi-Metal Oxide Nanoparticles Multi-metal oxide (MMO) nanomaterials have significant potential to facilitate various demanding (electro)catalytic reactions, but its intrinsic complexity hinders the in-depth understanding of the origin of the catalytic activity. In article number 2110857, Seoin Back, Seung-Ho Yu, Yung-Eun Sung, Taeghwan Hyeon, and co-workers report the structural understanding of uniform-sized spinel-type MMO nanoparticles, which boosts the electrocatalytic oxygen reduction reaction (ORR) activity. Physicochemical and electrochemical analyses reveal the contribution of each element to the structural flexibility and corresponding improved ORR activity.

Edge-enriched N, S co-doped hierarchical porous carbon for oxygen reduction reaction

The development of carbon materials with high electrochemical performance for next-generation energy device is emerging, especially N, S co-doped carbon materials have sparked intensive attention. However, the exploration of N, S co-doped carbon with well-defined active sites and hierarchical porous structures are still limited. In this study, we prepared a series of edge-enriched N, S co-doped carbon materials through pyrolysis of thiourea (TU) encapsulated in zeolitic imidazolate frameworks (TU@ZIF) composites, which delivered very good oxygen reduction reaction (ORR) performance in alkaline medium with onset potential of 0.94 V vs. reversible hydrogen electrode (RHE), good stability and methanol tolerance. Density functional theory (DFT) calculations suggested that carbon atoms adjacent to N and S are probable active sites for ORR intermediates in edge-enriched N, S co-doped carbon materials because higher electron density can enhance O2 adsorption, lower formation barriers of intermediates, improving the ORR performance comparing to intact N, S co-doped carbon materials. This study might provide a new pathway for improving ORR activity by the integration engineering of edge sites, and electronic structure of heteroatom doped carbon electrocatalysts.

Enhancing Oxygen Reduction Reaction Activity Using Single Atom Catalyst Supported on Tantalum Pentoxide

AbstractTransition metal oxides have emerged as promising cost‐effective alternatives to Pt catalysts for oxygen reduction reaction (ORR) in fuel cell applications. However, their low stability under harsh electrochemical conditions hinders their widespread applications. Tantalum pentoxide (Ta2O5) has proven to be a stable material under ORR conditions, but its activity is limited. In this work, we incorporate single atom catalysts (SACs) in Ta2O5 to resolve the limited ORR activity of this material by altering the electronic structures of surface Ta atoms. We use density functional theory (DFT) calculations to identify the most promising SACs with enhanced ORR activity. Pt, Rh, and Ir, are found to be the most promising SACs with improved ORR activity and high stability. This work suggests that SACs are effective in enhancing Ta2O5 catalytic activities for ORR.