Potential For Oxygen Reduction Reaction Research Articles

Cobalt@Ruthenium Core@Shell nanoparticles embedded within nitrogen-doped carbon nanosheets as reversible oxygen electrocatalysts

Rational design and engineering of cost-effective, high-performance reversible oxygen electrocatalysts for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is imperative in advancing the progress of rechargeable metal-air batteries (r-MABs). Herein, nanocomposites based on Co@Ru core@shell nanoparticles embedded within N-doped carbon nanosheets (Co@Ru/CS) are prepared via facile galvanic exchange reactions of RuCl3 with Co/NC and used as an effective oxygen electrocatalyst for rechargeable zinc-air battery (r-ZAB). Electrochemical studies demonstrate a remarkable bifunctional catalytic performance of Co@Ru/CS towards both ORR and OER, featuring a low potential gap (ΔE) of only 0.69 V between the OER potential (E10,OER) at 10 mA cm−2 and half-wave potential (E1/2,ORR) of ORR, which is much lower than that of commercial Pt/C + RuO2 catalysts (0.76 V). Combined studies of experimental characterizations and density functional theory calculations show that the ORR activity arises primarily from the N-doped carbon and CoNx moieties in the composites, whereas RuO2/CoOOH produced at high electrode potentials is responsible for the OER activity. Co@Ru/CS based r-ZAB exhibits an open circuit voltage of 1.447 V, specific capacity of 781 mAh gZn−1, and maximum power density of 115 mW cm−2 at 0.83 V, a performance better than that with commercial Pt/C + RuO2 (1.412 V, 760.56 mAh gZn−1, and 91 mW cm−2). Results from this research underline the substantial impact of structural engineering on optimizing the electrocatalytic activity of nanocomposites for r-MABs.

Axially Modified Square-Pyramidal CoN4-F1 Sites Enabling High-Performance Zn-Air Batteries.

Cobalt-nitrogen-carbon (Co-N-C) catalysts with a CoN4 structure exhibit great potential for oxygen reduction reaction (ORR), but the imperfect adsorption energy toward oxygen species greatly limits their reduction efficiency and practical application potential. Here, F-coordinated Co-N-C catalysts with square-pyramidal CoN4-F1 configuration are successfully synthesized using F atoms to regulate the axial coordination of Co centers via hydrothermal and chemical vapor deposition methods. During the synthesis process, the geometry structure of the Co atom converts from six-coordinated Co-F6 to square-pyramidal CoN4-F1 in the coordinatively unsaturated state, which provides an open binding site for the O2. The introduction of axial F atoms into the CoN4 plane alters the local atomic environment around Co, significantly improving the ORR activity and Zn-air batteries performance. In situ spectroscopy proves that CoN4-F1 sites strongly combine with the OOH* intermediate and facilitate the splitting of O-O bond, making OOH* readily decompose into O* and OH* via a dissociative pathway. Theoretical calculations confirm that the axial F atom effectively reduces the electronic density of the Co centers and facilitates the desorption of the OH* intermediate, efficiently accelerating the overall ORR kinetics. This work advances a feasible synthesis mechanism of axial ligands and provides a route to construct efficient high-coordination catalysts.

2D Metal Porphyrin-Based MOFs and ZIF-8 Composite-Derived Carbon Materials Containing M-Nx Active Sites as Bifunctional Electrocatalysts for Zinc-Air Batteries.

The main impediment to the development of zinc-air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Transition metal N-doped carbon catalysts offer a promising alternative to noble metal catalysts, with metal-organic framework (MOF)-derived carbon material catalysts being particularly noteworthy. Here, we synthesized MxP-Z-C carbon catalysts by combining two-dimensional (2D) metal porphyrin-based MOFs (MxPMFs, x = Fe, Co, Ni, Mn) and three-dimensional zeolitic imidazole framework-8 (ZIF-8) through electrostatic interaction, followed by carbonization. ZIF-8 was inserted between the layers of MxPMFs to prevent its Π-Π stacking, allowing the active sites to become fully exposed. MxP-Z-C demonstrated an impressive catalytic activity for both the ORR and the OER reactions. Among them, FeP-Z-C showed the best catalytic activity. The half-wave potential for ORR was 0.92 V (vs the reversible hydrogen electrode (RHE)), while the overpotential for the OER was 290 mV. In addition, the zinc-air battery assembled by FeP-Z-C exhibited high power density (133.14 mW cm-2) and significant specific capacity (816 mAh gZn-1), indicating considerable potential as a bifunctional catalyst for electronic devices.

Deciphering the linear relationship in the activity of the oxygen reduction reaction on Pt electrodes: A decisive role of adsorbates

Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction (ORR), the persistent challenge lies in the high onset overpotential of the ORR, and the effect of the electrolyte solution cannot be ignored. Consequently, we have systematically investigated the impact of adsorbate species and concentration, as well as solution pH, on the ORR activity on Pt(111) and Pt(poly) electrodes. The results all tend to establish a linear quantitative relationship between the onset potential for ORR and the adsorption equilibrium potential of the adsorbate. This finding indicates the decisive role of adsorbates in the onset potential for ORR, suggesting that the adsorption potential of adsorbates can serve as an intuitive criterion for ORR activity. Additional support for this conclusion is derived from experimental results obtained from the oxygen evolution reaction on Pt(poly) with different adsorbate species and from the hydrogen evolution reaction on Pt(111) with iodine adsorption. We further propose both an empirical equation for the onset potential for ORR and the concept of a potential-regulated adsorbate shielding effect to elucidate the influence of adsorbates on ORR activity. This study provides new insights into the high onset overpotential of the ORR and offers potential strategies for predicting and enhancing ORR activity in the future.

Molecular architectures of iron complexes for oxygen reduction catalysis—Activity enhancement by hydroxide ions coupling

Developing cost-effective and high-performance electrocatalysts for oxygen reduction reaction (ORR) is critical for clean energy generation. Here, we propose an approach to the synthesis of iron phthalocyanine nanotubes (FePc NTs) as a highly active and selective electrocatalyst for ORR. The performance is significantly superior to FePc in randomly aggregated and molecularly dispersed states, as well as the commercial Pt/C catalyst. When FePc NTs are anchored on graphene, the resulting architecture shifts the ORR potentials above the redox potentials of Fe2+/3+ sites. This does not obey the redox-mediated mechanism operative on conventional FePc with a Fe2+-N moiety serving as the active sites. Pourbaix analysis shows that the redox of Fe2+/3+ sites couples with HO- ions transfer, forming a HO-Fe3+-N moiety serving as the ORR active sites under the turnover condition. The chemisorption of ORR intermediates is appropriately weakened on the HO-Fe3+-N moiety compared to the Fe2+-N state and thus is intrinsically more ORR active.

Dual-axial engineering on atomically dispersed catalysts for ultrastable oxygen reduction in acidic and alkaline solutions

Atomically dispersed catalysts are a promising alternative to platinum group metal catalysts for catalyzing the oxygen reduction reaction (ORR), while limited durability during the electrocatalytic process severely restricts their practical application. Here, we report an atomically dispersed Co-doped carbon-nitrogen bilayer catalyst with unique dual-axial Co-C bonds (denoted as Co/DACN) by a smart phenyl-carbon-induced strategy, realizing highly efficient electrocatalytic ORR in both alkaline and acidic media. The corresponding half-wave potential for ORR is up to 0.85 and 0.77 V (vs. reversible hydrogen electrode (RHE)) in 0.5 M H2SO4 and 0.1 M KOH, respectively, representing the best ORR activity among all non-noble metal catalysts reported to date. Impressively, the Zn-air battery (ZAB) equipped with Co/DACN cathode achieves outstanding durability after 1,688 h operation at 10 mA cm-2 with a high current density (154.2 mA cm-2) and a peak power density (210.1 mW cm-2). Density functional theory calculations reveal that the unique dual-axial cross-linking Co-C bonds of Co/DACN significantly enhance the stability during ORR and also facilitate the 4e- ORR pathway by forming a joint electron pool due to the improved interlayer electron mobility. We believe that axial engineering opens a broad avenue to develop high-performance heterogeneous electrocatalysts for advanced energy conversion and storage.

Promoting the four electrocatalytic reactions of OER/ORR/HER/MOR using a multi-component metal sulfide heterostructure for zinc-air batteries and water-splitting.

Multi-component metal sulfide heterostructures are promising for multi-functional catalytic activities. In this work, we fabricated a multi-component metal sulfide heterostructure (Co-S-INF, composed of Co3S4 and (Fe, Ni)9S8) with nanoflower morphology clustered with numerous nanosheets by the electrodeposition of cobalt on iron-nickel foam followed by hydrothermal sulfurization treatment. Co-S-INF possesses high multi-functional electrocatalytic properties toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and methanol oxidation reaction (MOR). In particular, the ORR potential at 10 mA cm-2 is 0.682 V, and the OER, HER, and MOR potentials at 100 mA cm-2 are 1.478 V, 0.289 V, and 1.417 V, respectively. By using Co-S-INF, the aqueous ZAB with an ultrahigh peak power density of 332.30 mW cm-2 and an overall water splitting (OWS) device with a low splitting voltage of 1.82 V at 100 mA cm-2 can be obtained. In addition, the OWS potential can be further decreased to 1.70 V at a current density of 100 mA cm-2 with the assistance of MOR at the anode accompanying the production of the high value-added formate. Our work opens the way for the application and development of multi-functional electrocatalysts.

Exceptionally Bifunctional ORR/OER Performance via Synergistic Atom-Cluster Interaction.

The single-atom sites (SAs) have achieved enhanced performance toward oxygen reduction reaction (ORR) with the effective utilization of the active sites. However, the excess adsorption of the intermediates and the limited stability hinders performance improvement. Metal clusters with promising stability and weak adsorption can be used as potential substitutions, but the lack of active sites is considered undesirable for catalytic reactions. Herein, a framework of Fe nanoclusters combined with SAs on One dimensional (1D)carbon nanotubes (Fe3C-NCNTs 90minCC-1) is synthesized to confirm the synergistic atom-cluster interaction. The composite exhibits strong polarization and electron redistribution between nanocluster and SAs. The electron redistribution will significantly boost the electron transport and the desorption of the intermediates, which is confirmed by off-axis holography and DFT calculation. The electrocatalytic performance is significantly enhanced as the half-wave potential of ORR increased 75mV and the potential of OER increased 133mV compared with the sample without nanoclusters. Furthermore, such a bifunctional catalyst endows homemade Zn-air batteries (ZABs) with high power density and long-term stability. This work paves a facile route to design bifunctional ORR/OER electrocatalysts consisting of 0D composite structures.

Identifying Stable Electrocatalysts Initialized by Data Mining: Sb2 WO6 for Oxygen Reduction.

Data mining from computational materials database has become a popular strategy to identify unexplored catalysts. Herein, the opportunities and challenges of this strategy are analyzed by investigating a discrepancy between data mining and experiments in identifying low-cost metal oxide (MO) electrocatalysts. Based on a search engine capable of identifying stable MOs at the pH and potentials of interest, a series of MO electrocatalysts is identified as potential candidates for various reactions. Sb2 WO6 attracted the attention among the identified stable MOs in acid. Based on the aqueous stability diagram, Sb2 WO6 is stable under oxygen reduction reaction (ORR) in acidic media but rather unstable under high-pH ORR conditions. However, this contradicts to the subsequent experimental observation in alkaline ORR conditions. Based on the post-catalysis characterizations, surface state analysis, and an advanced pH-field coupled microkinetic modeling, it is found that the Sb2 WO6 surface will undergo electrochemical passivation under ORR potentials and form a stable and 4e-ORR active surface. The results presented here suggest that though data mining is promising for exploring electrocatalysts, a refined strategy needs to be further developed by considering the electrochemistry-induced surface stability and activity.

Reversibly Adapting Configuration in Atomic Catalysts Enables Efficient Oxygen Electroreduction.

Single-atom catalysts (SACs) featuring M-N-C moieties have garnered significant attention as efficient electrocatalysts for the oxygen reduction reaction (ORR). However, the role of the dynamic M-N configuration of SACs induced by the derived frameworks under applied ORR potentials remains poorly understood. Herein, we conduct a comprehensive investigation using multiple operando techniques to assess the dynamic configurations of Cu SACs under various microstructural interface (MSI) regulations by anchoring atomic Cu on g-C3N4 and zeolitic imidazolate framework (ZIF) substrates. Cu SACs supported on g-C3N4 exhibit symmetric Cu-N configurations characterized by a reversibly adaptive nature under operational conditions, which leads to their excellent ORR catalytic activity. In contrast, the Cu-N configuration in ZIF-derived Cu SACs undergoes irreversible structural changes during the ORR process, in which the elongated Cu-N pair is unstable and breaks during the ORR, acting as a competing reaction against the ORR and resulting in high overpotential requirements. Crucially, operando time-resolved X-ray absorption spectroscopy (TR-XAS) and Raman results unequivocally reveal the reversibly adapting properties of the local Cu-N configuration in atomic Cu-anchored g-C3N4, which have been overlooked in numerous literatures. All findings provide valuable insights into the potential-driven characteristics of atomic electrocatalysts during target reactions and offer a systematic approach to study atomic electrocatalysts and their corresponding catalytic behaviors.

A first principles analysis of potential-dependent structural evolution of active sites in Fe-N-C catalysts.

Fe-N-C (iron-nitrogen-carbon) electrocatalysts have emerged as potential alternatives to precious metal-based materials for the oxygen reduction reaction (ORR). However, the structure of these materials under electrochemical conditions is not well understood, and their poor stability in acidic environments poses a formidable challenge for successful adoption in commercial fuel cells. To provide molecular-level insights into these complex phenomena, we combine periodic density functional theory (DFT) calculations, exhaustive treatment of coadsorption effects for ORR reaction intermediates, including O and OH, and comprehensive analysis of solvation stabilization effects to construct voltage-dependent ab initio thermodynamic phase diagrams that describe the in situ structure of the active sites. These structures are further linked to activity and stability descriptors that can be compared with experimental parameters such as the half-wave potential for ORR and the onset potential for carbon corrosion and CO2 evolution. The results indicate that pyridinic Fe sites at zigzag carbon edges, as well as other edge sites, exhibit high activity for ORR compared to sites in the bulk. However, edges neighboring the active sites are prone to instability via overoxidation and consequent site loss. The results suggest that it could be beneficial to synthesize Fe-N-C catalysts with small sizes and large perimeter edge lengths to enhance ORR activity, while voltage fluctuations should be limited during fuel cell operation to prevent carbon corrosion of overoxidized edges.

Carbon-isolation induced indirect metal-metal interaction regulates the effect of hierarchical cobalt core on anchored palladium for bifunctional oxygen electrocatalysis

Herein, palladium (Pd)-anchored hierarchical structure metallic Co coated by nitrogen-doped carbon (Pd-NC/Co HS) is constructed as a bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). For Pd-NC/Co HS, the carbon shell isolates the metallic Co core from the electrolyte for avoiding corrosion, while the hierarchical metallic Co enhances the overall structural stability, mass transmission, and intrinsic electron transfer for beneficial electrocatalysis. Notably, the metallic Co core underneath carbon suitably tunes the microstructure of interface Pd nanocrystals, forming electron-deficient Pd2+ which is highly active for OER. Moreover, this carbon-isolation induced indirect metal–metal interaction (IMMI) between metallic Co core and Pd boosts the ORR of the hybrid Pd-NC/Co HS. Theoretical calculations further show that, compared to Pd/C, Pd-NC/Co HS possesses an obvious decreased energy barrier for ORR potential limiting step of *OH desorption and for OER potential limiting step of the conversion from *OH to *O, further confirming the appropriate regulation of Co on Pd via carbon shell. The zinc-air battery (168.25 mW/cm2) and magnesium-air battery (89.98 mW/cm2) driven by Pd-NC/Co HS deliver a higher peak power density than the one driven by precious metal catalysts, along with a longer operation time, showing promising application potentials.

Ni dispersed ultrathin carbon nanosheets as bi-functional oxygen electrocatalyst induced from graphite-like porous supramolecule

Excellent porosity and accessibility are key requirements during carbon-based materials design for energy conversion applications. Herein, a Ni-based porous supramolecular framework with graphite-like morphology (Ni-SOF) was rationally designed as a carbon precursor. Ultrathin carbon nanosheets dispersed with Ni nanoparticles and Ni-Nx sites (Ni@NiNx-N-C) were obtained via in-situ exfoliation during pyrolysis. Due to the hetero-porous structure succeeding from Ni-SOF, the Ni@NiNx-N-C catalyst showed outstanding bifunctional oxygen electrocatalytic activity with a narrow gap of 0.69 V between potential to deliver 10 mA cm−2 oxygen evolution and half-wave potential of oxygen reduction reaction, which even surpassed the Pt/C + IrO2 pair. Therefore, the corresponding zinc-air battery exhibited excellent power output and stability. The multiple Ni-based active sites, the unique 2D structure with a high graphitization degree and large specific surface area synergistically contributed to the excellent bifunctional electrocatalytic activity of Ni@NiNx-N-C. This work provided a novel viewpoint for the development of carbon-based electrocatalyst.

Nitrogen doping regulates microcrystal structure of interconnected Mn oxide particles/rods for oxygen reduction electrocatalysis

Manganese (Mn) oxide possessing considerable catalytic activity toward oxygen reduction reaction (ORR) exhibits promising potential in driving energy conversion technologies. However, small specific surface area, poor electron conductivity, and more importantly uncontrollable microgeometry of crystal greatly restraint their activity. Herein, a crystal regulation strategy induced by nitrogen doping is developed to construct interconnected Mn oxide nano-particles/rods (N-MnOx-Y) with different contents of [MnO6] octahedron for ORR. In N-MnOx-Y, "Y" refers to the mass ratio of melamine to α-MnO2 nanorods during calcination. Nitrogen doping induced increased content of crystalline [MnO6] octahedron is the primary factor boosting the intrinsic activity of N-MnOx-Y. The overall activity of N-MnOx-Y is also determined by electrochemically active area (ECSA) which is closely related to nitrogen doping. The crystal optimal N-MnOx-30 with high content of crystalline [MnO6] octahedron and large ECSA exhibits the highest half-wave potential for ORR and the largest kinetic current density (jk) among the N-MnOx-Y catalysts. When used as a cathodic catalyst, a homemade zinc-air battery driven by N-MnOx-30 delivers a peak power density higher than the one driven by Pt/C, along with better rate performance and a larger discharging specific capacity. This impressive electrocatalytic performance of N-MnOx-30 superior to Pt/C originates from the synergistic effect between crystalline [MnO6] octahedron, active area exposure, oxygen vacancy, Mn-N sites, and the three-dimensional hierarchical structure, which benefiting electronic/mass transmission and structural stability. This work offers a feasible strategy for constructing hierarchical and crystal tunable metal oxides electrocatalysts for efficient energy conversion.

Boosting the bifunctional electrocatalytic activity of nitrogen-doped graphene by electronic effect of heterovalent ion substituted perovskite oxides

Sluggish reaction kinetics of carbon-based catalysts hinder their activity in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which further impede commercialization of Zinc-air batteries. Here, a strategy of modifying the electronic structure of nitrogen-doped graphene (NG) through constructing it with cobalt (Co) substituted manganese-based perovskite oxides (LaMn1-xCoxO3) to accelerate its activity in OER and ORR is proposed. Co substitution is beneficial for donating electrons to oxygen-containing intermediates by inducing excessive negative charge on NG to improve kinetics in OER and ORR. The half-wave potential in ORR for LaMn0·6Co0·4O3@NG is 0.74 V, higher than that of LaMnO3@NG and LaCoO3@NG; the overpotential of LaMn0·6Co0·4O3@NG at 10 mA cm−2 is 314 mV for OER, smaller than that of LaMnO3@NG and LaCoO3@NG, supposing the superior electrochemical activity of composite catalyst with Co substitution in OER and ORR. This research offers a way in fabricating high efficient and cost-effective bifunctional electrocatalyst for Zinc-air batteries.

FeNC Catalysts with High Catalytic Activity and Stability for Oxygen Reduction Reaction

Although Pt-based catalysts have been considered as the most effective electrocatalyst for the cathodic oxygen reduction reaction (ORR) of direct methanol fuel cells (DMFCs), they still suffer from the drawbacks of high cost, poor long-term stability and methanol/ CO poisoning effects. Thus, developing low-cost ORR catalysts with high efficiency, durability and antipoisoning ability is of paramount importance. Herein, a series of non-noble metal FeNC materials are prepared through a facile pyrolysis process and used as the electrocatalysts toward ORR in alkaline electrolyte. Results show that the Fe0.50NC-800-1h catalyst pyrolyzed at 800 ºC for 1 h with the mass ratio of Fe(NO3)3•6H2O to melamine being 0.50 exhibits the highest catalytic performance among the as-prepared FeNC catalysts. The half-wave potential of ORR is ca. 0.81 V, which is only 38 mV lower than that on the noble metal Pt/C catalyst. Besides, it also displays higher stability and methanol tolerance than Pt/C. There is almost no change in the current during the chronoamperometric test when methanol is added in the electrolyte whereas significant decrease is found on Pt/C catalyst. This study of FeNC catalysts provides new insights on understanding the ORR mechanism and suggests a promising strategy to develop low-cost and highly efficient non-noble metal electrocatalysts for ORR.

MOF衍生的单原子催化剂中γN原子在ORR反应中的远程作用及其调制机制

The development of fuel cells is conducive to achieving carbon peaking and carbon neutrality goals, but the oxygen reduction reaction (ORR) of its cathodes is still kinetically slow due to multi-step proton-coupled electron transfer. Currently, metal-organic frameworks-derived single-atom catalysts (SACs) are emerging as efficient ORR catalysts. However, the outer layer structure of the active site is difficult to be determined, resulting in the uncertainty of the reaction mechanism. Here, the dual effect of the outer γN atom on its neighboring βC atom and the distant metal center was investigated. The results show that the doping of γN with different locations and amounts changes the electronic configuration of the replaced C sites in Fe-N4/C-γNx structures, which in turn affects the charge distribution of the βC atom closer to the metal center. And these changes indirectly affect the electron distribution and spin of the metal center through long-range effects, significantly enhancing the ORR performance of the 4-e− paths. More importantly, the electronegativity-enhanced βC atoms are thus more likely to adsorb the OH moiety in alkaline electrolyte typically used in experiments. Thus, a γN-modulated βC-assisted pathway was predicted and a higher thermodynamic limiting potential of ORR than that of the common 4-e− pathway was achieved. Further wavefunction analysis, based on the potential limiting steps, provided an understanding on the electronic level and revealed the significance of precise design and characteristics of γN site in analogous SACs.

Activity promotion of bifunctional catalysis by Se-doping and the application in rechargeable zinc-air batteries

Efficient bifunctional catalysts capable of catalyzing both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are required for the air electrode. Herein, the Se-doped FeNiP nanoparticles/N, P dual-doped carbon composite catalysts (FeNiP/SeNPC-2) were developed. The Se elements combine with various elements to form a compact heterogeneous material. At the same time, the Se-doping have modulated the crystal and surface structures, which have improved the catalytic activities of ORR and OER. The overpotential of OER was significantly negatively shifted, accompanied by a significant positive shift of the onset potential of ORR. FeNiP/SeNPC-2 has displayed an overpotential of 269 mV at the current density of 10 mA cm−2 for OER, and with a high half-wave potential (0.86 V) of ORR. The liquid zinc-air battery assembled using FeNiP/SeNPC-2 exhibited a power density of 171 mW cm−2 and stably charge-discharge cycled for 150 h. The solid-state zinc-air battery exhibited a power density of 88 mW cm−2 and stably charge-discharge cycled for 42 h. Subsequently, the solid-state zinc-air batteries of cylindrical hollow design are integrated as modules for driving devices.

Boosting the Electrocatalytic Performance of CoPt Alloy with Enhanced Electron Transfer via Atomically Dispersed Cobalt Sites.

Designing electrocatalysts with strong electronic metal-support interaction can effectively regulate the electronic properties of metal active centers, therefore maximizing the catalytic performance. As a proof of concept, heteroatoms doped carbon with CoPt alloy and isolated Co single atoms (CoPtCoSA@NSC) are synthesized using CoPt bimetallic metal-organic framework as the precursor in this work. The existence of CoSA on the carbon substrate leads to more electron transfer between CoPt and the support, and appropriate upward shift of the d band center of the catalysts, which can effectively reduce the reaction barrier of rate determine step and boost the catalytic performance of CoPt alloy. The enhanced catalytic activity and stability of CoPtCoSA@NSC are demonstrated experimentally. Remarkably, the overpotential for hydrogen evolution reaction is only 23mV at 10mAcm-2 and the half-wave potential for oxygen reduction reaction is 0.90V, both exceeding the commercial Pt/C benchmark. In addition, CoPtCoSA@NSC also exhibits great potential as a cathode electrocatalyst for Zn-air battery, in terms of large open circuit potential of 1.53V, high power density of 184mWcm-2 , as well as superior cycling stability. This work provides a novel strategy for regulating the electronic structure and catalytic performance of alloy based electrocatalysts.

Ag Anchored Atomically Around Nanopores of Porous Co(OH)2 for Efficient Bifunctional Oxygen Catalysis

AbstractVarious clean energy storage and conversion systems highly depend on rational design of efficient electrocatalysts for oxygen reactions. Increasing both gas molecular diffusion and intrinsic activity is critical to boosting its efficiency for bifunctional oxygen electrocatalysis. However, controllable synthesis of catalysts that combines gas molecular diffusion and intrinsic activity remains a fundamental challenge. Herein, a two‐step synthetic strategy is adopted to fabricate a composite oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional catalyst (P‐Ag‐Co(OH)2), of which, atomic Ag is anchored in reactive oxygen atoms around nanopores of Co(OH)2 nanosheets. Abundant nanopores provide enough gas molecular diffusion channels, and the special Ag‐O‐Co‐OH catalytic groups around nanopores display high intrinsic catalytic activity, which jointly result in an excellent ORR/OER performance. In alkaline electrolyte, P‐Ag‐Co(OH)2 displays a high half‐wave potential (0.902 V versus RHE) for ORR, and a low overpotential (235 mV at 10 mA cm−2) for OER, which is superior to non‐noble catalysts in previous studies and Pt/C (Ir/C) catalyst. At the same time, the single‐cell zinc‐air battery is prepared with an extremely high discharge peak power density of 435 mW cm−2 and excellent discharge–charge cycle stability.