Active Electrocatalysts Research Articles

Enhancing the Stability of Cu‐Based Electrocatalyst via Fe Alloy in Electrocatalytic Formaldehyde Oxidation with Long Durability

AbstractElectrocatalytic formaldehyde oxidation with metal Cu electrocatalyst has attracted significant interest since it can produce H2 at the anode and make it possible to construct a bipolar hydrogen production cell with low voltage. However, the activity of the Cu electrocatalyst will be greatly weakened after oxidizing it to Cu+ or Cu2+. Here, a CuFe bimetallic catalyst is developed to efficiently catalyze the electro‐oxidation process of HCHO to produce H2 at a potential of 0.10 VRHE with a current density of 100 mA cm−2. It is confirmed that introducing Fe in a CuFe catalyst can regulate the electron configuration to prevent Cu0 oxidation and improve the stability of the catalysts. The introduction of Fe can reduce the energy barrier of the reaction process, and make the C─H bond more easily split on CuFe. A bipolar hydrogen production device is constructed by combining the anodic oxidation of HCHO with the cathodic hydrogen evolution. The current density of 500 mA cm−2 is achieved at a cell voltage of 0.6 V. The faradaic efficiency is ≈100% and the device is stable for ≈50 h. The research provides a promising path toward the secure, effective, and expandable generation of high‐purity H2 at both anodic and cathodic electrodes.

Engineering Topological and Chemical Disorder in Pd Sites for Record-Breaking Formic Acid Electrocatalytic Oxidation.

Designing palladium-based formic acid oxidation reaction (FAOR) catalysts to achieve significant breakthroughs in catalytic activity, pathway selectivity, and toxicity resistance is both urgent and challenging. Here, these challenges are addressed by pioneering a novel catalyst design that incorporates both topological and chemical disorder, developing a new class of PdCuLaYMnW high-entropy amorphous alloys with a porous network (Net-Pd-HEAA) as a highly active, selective, and stable FAOR electrocatalyst. This novel Net-Pd-HEAA demonstrates record-breaking FAOR performance, achieving the mass and specific activities of 5.94 A mgPd -1 and 8.94mA cm-2, respectively, surpassing all previously reported Pd-based catalysts and showing strong competitiveness against advanced Pt-based catalysts. Simulataneously, Net-Pd-HEAA exhibits extraordinary stability in accelerated durability tests (ADT) and chronoamperometry (CA) tests. Advanced characterization and in situ, spectral analysis reveal that the extremely disordered atomic structure effectively regulates the geometric and electronic structure of the Pd sites, enhancing active intermediate coverage, facilitating dehydrogenation pathway, and inhibiting the production/adsorption of CO. Furthermore, when employed as the anode catalyst in proton exchange membrane water electrolysis (PEMWE), Net-Pd-HEAA only requires a potential of 1.28V to obtain a current density of 1 A cm-2, and operates stably in a highly corrosive electrolyte for over 100 h.

Enhanced Electrocatalytic Capacity of Two POM@NH2‐MIL‐101(Fe) Composites for Oxygen Evolution Reaction

AbstractThe development and exploration of efficient bifunctional electrocatalysts for water splitting are in high demand and have garnered significant attention in recent years. Herein, by incorporating the advantages of catalytically active polyoxometalates (POMs) and structural stable metal–organic frameworks (MOFs), two POM@MOFs composite materials, Ni4Mo12@Fe and Co4Mo12@Fe, have been successfully prepared via the encapsulation of POMs anions, [MoV12O30(μ2‐OH)10H2{NiII4(H2O)12}]∙14H2O (noted as Ni4Mo12) and [MoV12O30(μ2‐OH)10 H2{CoII(H2O)3}4]∙12H2O (noted as Co4Mo12), into the cavities of MOFs NH2‐MIL‐101(Fe), respectively. Compared to each individual components, Ni4Mo12@Fe and Co4Mo12@Fe composites, as heterogeneous electrocatalysts, both showed enhanced electrocatalytic capacities for efficient oxygen evolution reaction (OER) under alkaline conditions with overpotentials of 332.64 mV for Ni4Mo12@Fe and 352.64 mV for Co4Mo12@Fe at 10 mA cm−2. Additionally, the enhanced electrocatalytic capacities of these two composites could also achieve towards hydrogen evolution reaction (HER). Such a POMs‐assisted strategy for the formation of POM@MOFs composites, described here, paves a new avenue for the development of highly economical, active nonnoble metal bifunctional electrocatalysts for OER and HER.

Regulation of Oxide Pathway Mechanism for Sustainable Acidic Water Oxidation.

The advancement of acid-stable oxygen evolution reaction (OER) electrocatalysts is crucial for efficient hydrogen production through proton exchange membrane (PEM) water electrolysis. Unfortunately, the activity of electrocatalysts is constrained by a linear scaling relationship in the adsorbed evolution mechanism, while the lattice-oxygen-mediated mechanism undermines stability. Here, we propose a heterogeneous dual-site oxide pathway mechanism (OPM) that avoids these limitations through direct dioxygen radical coupling. A combination of Lewis acid (Cr) and Ru to form solid solution oxides (CrxRu1-xO2) promotes OH adsorption and shortens the dual-site distance, which facilitates the formation of *O radical and promotes the coupling of dioxygen radical, thereby altering the OER mechanism to a Cr-Ru dual-site OPM. The Cr0.6Ru0.4O2 catalyst demonstrates a lower overpotential than that of RuO2 and maintains stable operation for over 350 h in a PEM water electrolyzer at 300 mA cm-2. This mechanism regulation strategy paves the way for an optimal catalytic pathway, essential for large-scale green hydrogen production.

Fluorine-Induced Lattice Oxygen Participation in 2D Layered Double Hydroxide/MXene Hybrids for Efficient Oxygen Evolution.

In oxygen evolution reaction (OER), the participation of lattice oxygen can break the limitation of adsorption evolution mechanism, but the activation of lattice oxygen remains a critical challenge. Herein, a surface fluorinated highly active 2D/2D FeNi layered double hydroxide/MXene (F-LDH/MX) is demonstrated, boosting OER with the enhanced lattice-oxygen-mediated path. The introduction of fluorine promotes the self-evolution of catalyst in an alkaline environment, even without an external current. It further accelerates the formation of active metal oxyhydroxides with abundant oxygen vacancies under the operating potential. The introduced oxygen vacancy activates the lattice oxygen, increasing the proportion of lattice oxygen mechanism in OER. Owing to the synergistic effects of the 2D/2D hierarchical structure and the modulated active surface, F-LDH/MX possesses excellent electrochemical performances, including a low overpotential of 251 mV at 10 mA cm-2, a low Tafel slope of 40.28 mV dec-1, and robust stability. The water electrolyzer system with F-LDH/MX as the anode offers the benchmark current density at a low cell voltage of 1.53 V, while the Zn-air battery with F-LDH/MX as the air electrode exhibits a higher power density of 75.43 mW cm-2. This study presents a promising strategy to design highly active electrocatalysts for energy conversion and storage.

Synergistic Interplay between Fe-based Perovskite Oxides and Co in Electrolyte for Efficient Oxygen Evolution Reaction.

Perovskite oxides have been extensively investigated as active electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. While the OER activity of some perovskite oxides is positively influenced by Fe ions in the electrolyte, the impact of other transition metal ions in the electrolyte remains unclear. In this study, we compared the influence of Co ions intentionally added to the electrolyte on the OER activities of two Fe-based perovskite oxides (Ba0.5Sr0.5FeO3-δ and LaFeO3). While the OER activity ofBa0.5Sr0.5FeO3-δis significantly enhanced by adding Co ions to the electrolyte, LaFeO3 showed little difference in the OER behavior between the Co-free and Co-containing electrolytes. In the case of Ba0.5Sr0.5FeO3-δ, an amorphous layer was formed, and the Co ions from the electrolyte were incorporated on the surface as a result of OER cycling. On the other hand, Co ions were also detected on the surface ofLaFeO3, but its crystalline structure remains unchanged during the OER. Our study suggests that synergistic interplay between the perovskite oxides undergoing a structural transformation at the surface and transition metal ions in the electrolyte can improve the OER activity.

Aldehyde Directed In Situ Loading of Ag Nanodots Around the Open Metal Sites of MOFs for the Tandem Catalysis of Nitrate to Ammonia.

Both spatial arrangement and intrinsic activity of electrocatalysts with dual-active sites are widely designed to match the coupling reaction between nitrate and water, in which most of the reactive intermediates can be optimized to achieve a high yield rate of ammonia. Herein, by introducing the aldehyde group inside metal-organic frameworks (MOFs) in advance, an aldehyde-induced method is achieved to direct the in situ nucleation of Ag nanodots depending on the mesopores of MOFs via a simple silver mirror reaction. The key point here is that the spatial arrangement between the aldehyde group and open metal sites is fixed end to end, which makes the aldehyde group a built-in redox-active site to drive the in situ nucleation of Ag nanodots next to the open metal sites of MOFs. Accordingly, by varying the metal sites of MOFs, a group of M-MOFs@Ag (M = Fe, Co, Ni, Cu, etc.) hybrids with dual active sites are acquired. Taking Ni-MOFs@Ag as an example, the interaction between Ni2+ and Ag sites makes it available for the tandem catalysis of nitrate-to-ammonia, in which the H· and NO2 - generated on the open Ni2+ sites and Ag nanodots, respectively, can migrate to each other to evolve into ammonia.

Selective Self‐Assembly of Atomically Dispersed Iron and Cobalt Dual Atom Catalyst on Anisotropic Mesoporous Carbon Particles for High Performance Seawater Batteries

AbstractNa‐seawater batteries (SWBs) are environmentally friendly energy storage system that utilizes abundant seawater as an electrolyte alternative to conventional distilled water‐based and organic electrolytes. To achieve high energy efficiency in Na‐SWBs, it is necessary to enhance the activity of bifunctional oxygen electrocatalysts. In this study, an atomically dispersed iron and cobalt dual‐atom nitrogen‐doped lens‐shaped mesoporous carbon (FeCo‐LMC) particles is synthesized as a SWB cathode material using the spinodal decomposition of the polymer blend and selective precursor positioning. The well‐aligned mesoporous structure and synergetic effect of the dual‐atom site realize FeCo‐LMC as a comparable bifunctional oxygen catalyst with the lowest overpotential difference (EOER−EORR) among the other catalysts with natural seawater electrolyte. When applied to the SWB system, the FeCo‐LMC shows a highly improved charge/discharge performance compared to Pt/C and a stable cycling performance for 200 h. Density functional theory calculations reveal the enhanced oxygen catalytic activity of FeCo‐LMC owing to electron delocalization and d‐band center adjustment of FeN4–CoN4 structure.

Theoretical Investigation of Single-, Double-, and Triple- p-block Metals Anchored on g-CN Monolayer for Oxygen Electrocatalysis.

The design and development of highly active non-noble metal electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are crucial for metal-air batteries. In this work, the electrocatalytic performance of different p-block metal (PM = Sn, Sb, Pb and Bi) atoms embedded in the g-CN monolayer (PMx@g-CN, x = 1-3) for the OER and ORR was systematically investigated by density functional theory (DFT). The strong interaction between PMx atoms and g-CN substrates indicates the good stability of PMx@g-CN catalysts. Among all the designed catalysts, Bi3@g-CN is found to be a promising bifunctional electrocatalyst for both the OER and ORR with the calculated overpotential ηOER and ηORR of 0.23 and 0.25 V, respectively. With the atomic active sites of PMx increasing from x = 1 to 3, the OER and ORR catalytic activity is enhanced. The correlations between the overpotentials of the OER/ORR and Bader charge values of the anchored PMx atoms of the catalysts were established. Our findings contribute to searching for noble metal-free bifunctional electrocatalysts and shed light on the rational design of atomic active sites on electrocatalysts.

Visualizing the Structure and Dynamics of Transition Metal-Based Electrocatalysts Using Synchrotron X-Ray Absorption Spectroscopy.

As the global energy structure evolves and clean energy technologies advance, electrocatalysis has become a focal point as a critical conversion pathway in the new energy sector. Transitional metal electrocatalysts (TMEs) with their distinctive electronic structures and redox properties show great potential in electrocatalytic reactions. However, complex reaction mechanisms and kinetic limitations hinder the improvement of energy conversion efficiency, highlighting the necessity for comprehensive studies on structure and performance of electrocatalysts. X-ray Absorption Fine Structure (XAFS) spectra stand out as a robust tool for examining the electrocatalyst's structures and performance due to its atomic selectivity and sensitivity to local environments. This review delves into the application of XAFS technology in characterizing TMEs, providing in-depth analyses of X-ray Absorption Near-Edge Structure (XANES) spectra, and Extended XAFS (EXAFS) spectra in both R-space and k-space. These analyses reveal intrinsic structural information, electronic interactions, catalyst stability, and aggregation morphology. Furthermore, the paper examines advancements in in-situ XAFS techniques for real-time monitoring of active site changes, capturing critical intermediate and transitional states, and elucidating the evolution of active species during electrocatalytic reactions. These insights deepen our understanding on structure-activity relationship of electrocatalysts and offer valuable guidance for designing and developing highly active and stable electrocatalysts.

Surface-Reconstructed CdNNi3 Antiperovskite Electrocatalyst: Unlocking Ampere-Level Current Density for Hydrogen Evolution.

Developing conductive electrocatalysts is crucial for decreasing the ohmic loss induced by electric resistance of the catalyst layer in the large-current-density hydrogen evolution reaction (HER), which has been overlooked previously. In this study, we screen a highly conductive antiperovskite CdNNi3 with negligible ohmic loss, as a highly active and durable HER electrocatalyst capable of unlocking ampere-scale current densities. CdNNi3 exhibits an impressive activity (an overpotential of 235 mV) at 1 A cm-2 and maintains its performance steadily at an ampere-scale current density (at 1 A cm-2 over 400 h). Besides, the CdNNi3-enabled anion-exchange membrane water electrolyzer outperforms that of the benchmark Pt/C, evidenced by a reduced cell voltage of 160 mV at 1 A cm-2, and presents a favorable stability at 1 A cm-2. Importantly, this study experimentally discovers the dynamic surface reconstruction phenomena of antiperovskite nitrides during alkaline HER. Theoretical analysis suggests that the presence of Cd in the reconstructed surface effectively adjusts the local electronic configuration of active sites, which promotes the adsorption of OH and reduces the binding strength to H, thereby facilitating the water dissociation step and reducing the energy barrier of the potential-determining step in the HER process.

High-Entropy Prussian Blue Analogue Derived Heterostructure Nanoparticles as Bifunctional Oxygen Conversion Electrocatalysts for the Rechargeable Zinc-Air Battery.

In response to energy challenges, rechargeable zinc-air batteries (RZABs) serve as an ideal platform for energy storage with a high energy density and safety. Nevertheless, addressing the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in RZAB requires highly active and robust electrocatalysts. High-entropy Prussian blue analogues (HEPBAs), formed by mixing diverse metals within a single lattice, exhibit enhanced stability due to their increased mixing entropy, which lowers the Gibbs free energy. HEPBAs innately enable sacrificial templating, an effective way to synthesize complex structures. Impressively, in this study, we successfully transform HEPBAs into exquisite multiphase (multimetallic alloy, metal carbide, and metal oxide) heterostructure nanoparticles through a controlled synthesis process. The elusive multiphase heterostructure nanoparticles manifested two active sites for selective ORR and OER. By integrating CNT into HEPBA-derived nanoparticles (HEPBA/CNT-800), the HEPBA/CNT-800 demonstrates superior activity toward both ORR (E1/2 = 0.77 V) in a 0.1 M KOH solution and the OER (η = 330 mV at 50 mA cm-2) in a 1 M KOH solution. The RZAB with a HEPBA/CNT-based air electrode demonstrated an open-circuit voltage of 1.39 V and provided a significant energy density of 71 mW cm-2. Moreover, the charge and discharge cycles lasting up to 40 h at a current density of 5 mA cm-2 demonstrate its excellent stability. This work provides an alternative avenue for the rational design of HEPBA's derivative for a sustainable rechargeable metal-air battery platform.

Wet sulfuration of molybdate and reconstruction regulation of trace Fe doping for oxygen evolution

There is a growing interest in the development of active, durable, and cost-effective electrocatalysts for oxygen evolution reactions (OER). In this study, we synthesized a self-reconstruction iron-doped sulfide-regulated nickel molybdate catalyst using wet chemical sulfuration and electrodeposition techniques. The core-shell nanorods (SC@NMO) were produced through rapid sulfuration. We investigated the effects of sulfur leaching on rapid and extensive electrochemical self-reconstruction. Our approach utilized the phase change of Fe3+ and electrodeposition-induced restructuring to enhance the catalyst's OER activity and stability in an alkaline electrolyte. Notably, iron ions establish a precipitation-dissolution dynamic equilibrium at the interface between the catalyst surface and the electrolyte, which minimizes iron loss and results in a more efficient and stable catalyst. The prepared sample, SC-Fe(Ni)OOH@NMO, demonstrated exceptional oxygen evolution performance and long-term stability in a 1 M KOH solution, achieving an overpotential of only 279 mV at a current density of 100 mA cm−2. It maintained stable operation for 200 h in a high-concentration 6 M KOH solution. The above data prove that this work provides a feasible strategy to enhance the OER catalytic capacity of metal oxides by the two modification methods of co-doping of metal and non-metal and reconstruction.

Boosting multi-carbon products selectivity of carbon dioxide reduction via bifunctional cyclodextrin-modification on copper/copper(I) oxide electrocatalysts

Electrochemical carbon dioxide reduction to multi-carbon (C2+) products presents a significant opportunity for converting greenhouse gases into valuable fuels and feedstocks. The development of highly active and stable catalysts remains a critical challenge. In this study, we report the design and synthesis of cyclodextrin-modified Cu/Cu2O electrocatalysts, which exhibit remarkable efficiency in driving the CO2 electroreduction process towards C2+ products. Our optimized catalyst achieves a C2+ Faradaic efficiency exceeding 50 % at a high current density of over 200 mA cm−2. Experimental findings, supported by density functional theory (DFT) calculations, reveal that cyclodextrin plays a dual role in stabilizing Cu+ and increasing the surface density of hydroxyl radicals. This dual function greatly benefits for enhancing *CO intermediate adsorption and promotes *CHO formation, thereby facilitating the crucial dimerization step for the formation of C2+ products. This work provides valuable insights into the development of highly active and selective electrocatalysts by carefully tuning the local catalytic environment, potentially opening new avenues for functionalizing electrocatalysts for future research in this area.

Boron doped Fe3S4/Co3S4 decorated with multi-wall carbon nanotubes as an efficient electrocatalyst for oxygen evolution reaction in alkaline media

Designing an exceedingly active and universal electrocatalyst for oxygen evolution reaction is utterly essential for commercial development. Herein, boron-doped cobalt-iron bimetallic sulfide synthesized through an easy single-step hydrothermal route is reported as electrocatalyst. The B-Fe3S4/Co3S4 was further decorated with the multi-wall carbon nano-tubes (MWCNT). The morphology of B-Fe3S4/Co3S4 was sphere like and it was converted to marigold flower-like after decorating it with MWCNT. The catalytic efficiency of Fe3S4/Co3S4 increased by doping with Boron and further increased by decorating with MWCNT. The prepared catalyst B-Fe3S4/Co3S4/MWCNT was tested for oxygen evolution reaction (OER) in alkaline solution and offered 319mV as overpotential and 60mV/decas Tafel slope value. In addition to it, the catalyst shows good stability, large Brunauer - Emmett-Teller (BET) surface area (30.24 m2/g), and low value of charge transfer resistance (6.5Ω), indicating that it is efficient catalyst and its high efficiency is associated with its morphology and ternary composite structure. The investigated low cost catalyst is as good as the commercially used high cost noble metal RuO2 catalysts.

Amorphous CoFePOx hollow nanocubes decorated with g-C3N4 quantum dots to achieve efficient electrocatalytic performance in the oxygen evolution reaction.

Simultaneously enriching active sites and enhancing intrinsic activity in a simple way is of great importance for the design of highly active electrocatalysts for the oxygen evolution reaction (OER), but it still faces challenges. Herein, g-C3N4 quantum dot decorated amorphous hollow CoFe bimetallic phosphate nanocubes (a-CoFePOx@CNQD) are prepared as an efficient OER electrocatalyst by a simple in situ etching-phosphating process. Research shows that their unique hollow architecture and amorphous structure can help provide generous exposed active sites for OER, and the incorporation of g-C3N4 quantum dots can effectively adjust the electronic structure to improve the intrinsic activity. Therefore, a-CoFePOx@CNQD exhibits excellent OER performance with a low overpotential (239 mV) at 10 mA cm-2 and a small Tafel slope (58.4 mV dec-1), surpassing the commercial RuO2. Furthermore, a-CoFePOx@CNQD as an electrode catalyst for a water electrolyzer and zinc-air battery also shows higher performance and stability than RuO2 + Pt/C catalysts. This study provides a feasible strategy for preparing efficient and stable amorphous hollow heterostructure OER electrocatalysts.

Ex Situ Electro‐Organic Synthesis – A Method for Unrestricted Reaction Control and New Options for Paired Electrolysis

AbstractClassic in situ electro‐organic synthesis with substrates in an electrolyzer must compromise process conditions to balance electro‐ and thermochemical steps at both electrodes. This often restricts efficiency and product selectivity, since requirements may deviate for electrochemical (catalyst activation) and chemical (organic synthesis) steps, as well as for paired anode‐ and cathode reactions. Breaking this barrier, we report ex situ electro‐organic synthesis as a versatile method that enables unique product selectivity and unusual product pairs. We exemplify the concept for pairing H2 evolution (HER) with anodic alcohol oxidation. The two‐step method accomplishes this by separating cathode reactions from organic substrate oxidation, and anodic electrocatalyst activation from chemical conversion of organic substrates in time and space. First, the electro‐oxidation of Ni(OH)2 anodes to NiOOH is paired with H2 production by alkaline water electrolysis. Then, “charged” NiOOH electrodes are removed from the electrolyzer and used in external vessels to oxidize model substrate benzyl alcohol under regeneration of Ni(OH)2. Free choice of reaction media outside the electrolyzer allows to selectively obtain benzoic acid (in water) or benzaldehyde (in n‐hexane), whereas classic in situ electrosynthesis only produces the acid together with H2. Perspectively, the method enables electrosynthesis of previously inaccessible products paired to H2 generation.

Effects of carbon support ozonation on the electrochemical reduction of CO2 to formate and syngas in a flow cell on Pd nanostructures

Pd convers electrochemically CO2 into formate at the most positive known potentials but with low activity. Additionally, Pd is CO selective at more negative potentials, but is poisoned by the strongly bound CO∗ intermediate. Improving the activity and stability of Pd-based electrocatalysts holds promise for improving the electrochemical production of formic acid. Herein, we studied the effects of carbon support and its ozonation on the selectivity of electrochemical CO2 reduction on Pd. The ozone treatment is found to improve the activity and formate selectivity at low overpotentials on single-walled carbon nanotube-supported catalysts with partial current densities up to −12 mA cm−2 in 0.5 M KHCO3 at potentials of −0.35 V and −0.45 V (vs. RHE). At more negative potentials, the catalysts become more selective towards CO and an opposite trend for CO-selectivity and ozonation duration is demonstrated. Unfortunately, the materials show deactivation in the form of decreased formate selectivity and increased hydrogen and CO evolution, especially when supports treated with ozone for a longer duration. The results and possible mechanisms are discussed based on previous findings and the physicochemical characterizations of the prepared catalysts. This work shows that a simple ozone treatment of carbons changes the efficiency of CO2 electroreduction.

Cobalt Nitride-Implanted PtCo Intermetallic Nanocatalysts for Ultrahigh Fuel Cell Cathode Performance.

Stable and active oxygen reduction electrocatalysts are essential for practical fuel cells. Herein, we report a novel class of highly ordered platinum-cobalt (Pt-Co) alloys embedded with cobalt nitride. The intermetallic core-shell catalyst demonstrates an initial mass activity of 0.88 A mgPt-1 at 0.9 V with 71% retention after 30,000 potential cycles of an aggressive square-wave accelerated durability test and loses only 9% of its electrochemical surface area, far exceeding the US Department of Energy 2025 targets, with unprecedented stability and only a minimal voltage loss under practical fuel cell operating conditions. We discover that regulating the atomic ordering in the core results in an optimal lattice configuration that accelerates the oxygen reduction kinetics. The presence of cobalt nitride decorated within PtCo superlattices guarantees a larger barrier to Co dissolution, leading to the excellent endurance of the electrocatalysts. This work brings up a transformative structural engineering strategy for rationally designing high-performing Pt-based catalysts with a unique atomic configuration for broad practical uses in energy conversion technology.

Mechanistic Study of Highly Active Bifunctional Double-Atom Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reactions.

Dual-atom catalysts (DACs) can be very effective for catalyzing both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we present theoretical evidence of a new class of highly active DACs, namely, the double-atom embedded in nitrogen-doped graphene sheet 2M-N-C (M = Mn, Fe) on the basis of density functional theory calculations. Importantly, we find that the double active sites of 2M-N-C DACs entail an unconventional catalytic reaction pathway for ORR and OER. We also show that the local coordination environment of the active sites can significantly affect the stability and oxygen catalytic activity of 2M-N-C DACs. In particular, MnFe-N-C DAC not only exhibits good stability but also possesses outstanding bifunctional ORR/OER catalytic activity with the potential difference (ΔE) between the OER and ORR as low as 0.34 V, notably lower than most bifunctional electrocatalysts reported in the literature. This finding suggests a new strategy toward the design of stable and highly active bifunctional electrocatalysts for both ORR/OER.