Outstanding Oxygen Reduction Reaction Research Articles

Boosting the O2-to-H2O2 Selectivity Using Sn-Doped Carbon Electrocatalysts: Towards Highly Efficient Cathodes for Actual Water Decontamination.

The high cost and often complex synthesis procedure of new highly selective electrocatalysts (particularly those based on noble metals) for H2O2 production are daunting obstacles to penetration of this technology into the wastewater treatment market. In this work, a simple direct thermal method has been employed to synthesize Sn-doped carbon electrocatalysts, which showed an electron transfer number of 2.04 and outstanding two-electron oxygen reduction reaction (ORR) selectivity of up to 98.0 %. Physicochemical characterization revealed that this material contains 1.53 % pyrrolic nitrogen, which is beneficial for the production of H2O2, and -C≡N functional group, which is advantageous for H+ transport. Moreover, the high volume ratio of mesopores to micropores is known to favor the quick escape of H2O2 from the electrode surface, thus minimizing its further oxidation. A purpose-made gas-diffusion electrode (GDE) was prepared, yielding 20.4 mM H2O2 under optimal electrolysis conditions. The drug diphenhydramine was selected for the first time as model organic pollutant to evaluate the performance of an electrochemical advanced oxidation process. In conventional electro-Fenton process (pH 3), complete degradation was achieved in only 15 min at 10 mA cm-2, whereas at natural pH 5.9 and 33.3 mA cm-2, almost overall drug removal was reached in 120 min.

Defective carbon-bridged Cu sites to boost oxygen reduction reaction in neutral zinc-air batteries

Novel carbon nanomaterials containing N-coordinated metal centers present an advantage in promoting the oxygen reduction reaction (ORR). Despite considerable progress, substantial challenges persist with the advancement of neutral Zinc-air batteries (ZABs), particularly in optimizing the trade-off between the catalytic activity and stability. Herein, employing nanoporous carbon impregnated with Cu(II)-phenanthroline complexes to prepare Cu-ONCs catalysts rich in Cu-Nx sites. Controllable carbon defects to capture Cu2+ enable the enrichment of metal sites on the porous carbon surface, and simultaneously effectively suppress the aggregation of active centers. The metal moieties, specifically Cu-Nx, are incorporated into the porous N-doped carbon, thereby introducing accessible active sites within the partially graphitized carbon framework. Furthermore, the abundant mesopores inside the carbon nanofibers promote the exposure of accessible active sites to substantially augment the electrochemically active electrochemically active area area. Given the unique structure and composition, Cu-ONCs show outstanding ORR activity in neutral and alkaline media, alone with negligible decay observed after 3000 cycles. Moreover, Cu-ONCs based neutral ZABs demonstrate a peak power density of 48.28 mW cm−2 and impressive rate performance. This work provides defects/vacancies insight on transition metal (TM)-based carbon support to facilitate the advancement of cutting-edge neutral ZABs.

Boosting electrocatalytic oxygen reduction of Fe-Co polyphthalocyanine via the synergy of metal component optimization and axial ligand modification

Conjugated metal polyphthalocyanine (MPPc) organic skeletons, a kind of novel porous materials containing inherent M−N4 highly active sites, are of great significance for oxygen reduction reaction (ORR). Herein, bimetallic Fe-Co phthalocyanine covalent polymers (denoted as FeCoPPc) were prepared as ORR electrocatalysts through a solvothermal process and subsequent oxidation treatment. Meanwhile, the effect of axial oxygen-containing ligands of metal centers on the catalytic kinetic processes was also investigated. Benefiting from the highly exposed bimetal active sites and the finely designed ligand structure, FeCoPPc with optimized Fe/Co ratio and ClO3− coordination (Fe0.9Co0.1PPc-ClO3) displayed an outstanding ORR electrocatalytic activity and superior durability compared to 20 % Pt/C, manifested by an onset potential of 0.986 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.923 V vs. RHE in a 0.1 M KOH solution. This work may guide the rational design of high-performance electrocatalysts to regulate the catalytic activity.

Fe3O4 encapsulated in hierarchically porous nitrogen-doped graphitic carbon layers for efficient oxygen reduction reaction: Enhanced intrinsic activity via directional interfacial charge transfer

Constructing efficient electrocatalysts for the oxygen reduction reaction (ORR) is crucial for the commercialization of metal-air batteries. Iron oxide-based catalysts exhibit promising potential for ORR. However, addressing the issue of inferior catalytic performance is essential, and a comprehensive understanding of the catalytic mechanism of iron oxide-based catalysts is also lacking. In this study, we present Fe3O4 nanoparticles encapsulated in N-doped graphitic carbon layers (NGC) hosted by hierarchically porous carbon (Fe3O4@NGC), achieved through a facile dual melt-salt template strategy. The encapsulation of Fe3O4 nanoparticles protects them from corrosion and exfoliation, endowing the catalysts with superior stability. Density functional theory (DFT) calculations discover that the electronic interaction between Fe3O4 nanoparticles and N-doped graphitic carbon layers induces directional interfacial electron transfer, which effectively modulates the surface electronic structure to improve the binding ability to O2, weaken the OO bond, and optimize the adsorption of intermediates, thus boosting the intrinsic activity. DFT unveils that the C atoms nearest to graphitic-N in NGC are active sites. Finally, the synergistic effects of Fe3O4 nanoparticles and NGC result in outstanding ORR performance and superior stability and methanol tolerance of Fe3O4@NGC, with a half-wave potential of 0.89 V, surpassing that of Pt/C by 50 mV. Fe3O4@NGC also shows better performance than Pt/C when used as the air-electrode catalyst in zinc-air battery.

Synergistic effects of carbon nanotubes on α-MnO2 electrocatalysts for improved oxygen reduction in alkaline fuel cells

The Alkaline Membrane Fuel Cell (AMFC), is a device crucial for electrochemical energy production through the oxygen reduction reaction (ORR), conventionally relies on platinum catalysts. However, the challenges of excessive cost and inadequate stability in alkaline environments have hindered its widespread commercialization. Alpha manganese dioxide (αMnO2), with diverse applications in energy and environmental domains, has potential as an alternative catalyst due to its lower metal costs and comparable catalytic activity. This study focuses on the synthesis of αMnO2 nanotubes through controlled environment temperature, and integration with carbon nanotubes (CNTs). Optimizing the gas pressure and temperature during synthesis resulted in structural changes in αMnO2 nanotubes, with a notable increase in catalytic behavior at elevated temperatures. The sample treated at 450 °C and mixed with CNTs (CNT-MO450) demonstrated outstanding ORR performance and prolonged stability in an alkaline medium. Furthermore, the CNT-MO450 exhibited the highest current density of −5.2 mA/cm2 at a potential of 0.65 V vs RHE, a peak power density of 73 mW/cm2 (comparable to Pt/C at 95 mW/cm2), and a charge transfer resistance of 310 Ω. The temperature treatment affected the αMnO2 nanotubes, which resulted in increased length at an optimal temperature, leading to a larger surface area. This enhancement in surface area is crucial to improved catalytic activity, electrical conductivity, and extended stability during operation in alkaline media. The findings suggest that CNT-MO450 catalysts hold promise as a cost-effective and stable alternative catalyst for AMFCs.

Microenvironment Tailoring of NiCo Alloys Coupled with FePc as Efficient Bifunctional Catalysts for High-Rate Zn-Air Batteries.

The practical application of Zn-air batteries require exploring cost-effective and durable bifunctional electrocatalysts. However, the simultaneous preparation of catalysts with bifunctional activities for oxygen reduction reaction (ORR) and oxygen precipitation reaction (OER) remains challenging. Herein, we synthesized a novel hybrid catalyst (FePc/NiCo/CNT), which couples NiCo alloy with FePc through electrostatic interaction. The interaction between FePc and NiCo alloy can enhance the intrinsic catalytic activity of the active site Fe-N4 and prevent the electrolyte corrosion of the metal alloy, ultimately improving the stability of the catalyst by the microenvironment-tailoring strategy. The resultant FePc/NiCo/CNT catalyst exhibits outstanding oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V, which is attributed to the abundant Fe-Nx active sites. Furthermore, the electron interactions between NiCo/CNT and FePc accelerate electron transfer and enhance the activation of oxygen intermediates, consequently boosting the OER activity with an overpotential of 260 mV at 10 mA cm-2. The Zn-air batteries assembled with FePc/NiCo/CNT show a high power density of 175.1 mW cm-2 and excellent cycling stability for up to 430 h at 20 mA cm-2. The preparation of oxygen electrode catalysts for renewable clean energy devices can be made more convenient with this directly engineered strategy for ORR and OER active centers.

Precisely Designed Morphology and Surface Chemical Structure of Fe-N-C Electrocatalysts for Enhanced Oxygen Reaction Reduction Activity.

Fe-N-C materials have been regarded as one of the potential candidates to replace traditional noble-metal-based electrocatalysts for the oxygen reduction reaction (ORR). It is believed that the structure of carbon support in Fe-N-C materials plays an essential role in highly efficient ORR. However, precisely designing the morphology and surface chemical structure of carbon support remains a challenge. Herein, we present a novel synthetic strategy for the preparation of porous carbon spheres (PCSs) with high specific surface area, well-defined pore structure, tunable morphology and controllable heteroatom doping. The synthesis involves Schiff-based polymerization utilizing octaaminophenyl polyhedral oligomeric silsesquioxane (POSS-NH2) and heteroatom-containing aldehydes, followed by pyrolysis and HF etching. The well-defined pore structure of PCS can provide the confinement field for ferroin and transform into Fe-N-C sites after carbonization. The tunable morphology of PCS can be easily achieved by changing the solvents. The surface chemical structure of PCS can be tailored by utilizing different heteroatom-containing aldehydes. After optimizing the structure of PCS, Fe-N-C loading on N,S-codoped porous carbon sphere (NSPCS-Fe) displays outstanding ORR activity in alkaline solution. This work paves a new path for fabrication of Fe-N-C materials with the desired morphology and well-designed surface chemical structure, demonstrating significant potential for energy-related applications.

Designing Highly Efficient Electrocatalyst for ORR and OER Based on Nb2CO2 MXene: The Role of Transition Metals and N-Doping Content.

Finding efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative for advancing zinc-air batteries. Herein, the effect of transition metal anchored on Nb2CO2 with different N content to form TM-Nx-Nb2CO2 on the catalytic activity of ORR and OER is investigated by density functional theory. Among all the designed TM-Nx-Nb2CO2, Pt-N12.50%-Nb2CO2, Pt-N37.50%-Nb2CO2, Pt-N50.00%-Nb2CO2, Pd-N68.75%-Nb2CO2, and Pd-N100%-Nb2CO2 are excellent ORR electrocatalysts with ηORR values of 0.38, 0.36, 0.38, 0.38, and 0.34 V, respectively. Rh-Nb2CO2, Rh-N12.50%-Nb2CO2, Rh-N31.25%-Nb2CO2, Rh-N37.50%-Nb2CO2, Rh-N50.00%-Nb2CO2, Pt-N50.00%-Nb2CO2, Rh-N68.75%-Nb2CO2, and Rh-N81.25%-Nb2CO2 are excellent OER electrocatalysts with ηOER values of 0.33, 0.37, 0.34, 0.36, 0.37, 0.34, 0.38, and 0.33 V, respectively. Notably, Rh-Nb2CO2 and Pt-N50.00%-Nb2CO2 exhibit outstanding ORR and OER bifunctional catalytic activity with potential gap values of 0.80 and 0.72 V, respectively, which are higher than the activities of most reported bifunctional catalysts. Furthermore, electronic structure analysis indicates that the moderate adsorption strength of oxygen-containing intermediates on active centers is crucial for achieving highly active bifunctional catalysts for ORR and OER. This study provides a strategy for the design of novel ORR and OER catalysts using 2D MXene materials.

Engineering Synergetic Fe‐Co Atomic Pairs Anchored on Porous Carbon for Enhanced Oxygen Reduction Reaction

AbstractThe rational design of heteronuclear dual‐atom catalyst (DAC) is intricate due to the random dispersion of metal atoms under thermal treatment. Herein, a novel precursor pre‐orientation strategy is reported to construct Fe‐Co diatomic sites atomically dispersed on nitrogen doped carbon (Fe‐Co‐NC) via cubic Prussian blue analogue as metal source. Due to the specific synergy between Fe and Co centers, the obtained Fe‐Co‐NC catalyst renders outstanding oxygen reduction reaction (ORR) performance with positive half‐wave potential and good durability in wide pH range. Density functional theory further clarifies the active centers and reveals that the Fe‐Co‐NC dual atomic catalyst follows the modulation mechanism, where the intermediates tended to adsorb on Fe site, while the neighboring Co atom can assist by lowering the d‐band center of Fe site. Experimentally and theoretically emphasizes the priority of heteronuclear diatomic Fe‐Co catalysts over homonuclear Fe‐Fe‐NC and Co‐Co‐NC DAC. Moreover, the Zn‐Air battery (ZAB) and microbial fuel cell (MFC) assembled with Fe‐Co‐NC cathodes both exhibit splendid power density (382 mW cm−2 for ZAB, 2034 ± 103 mW m−2 for MFC) as well as excellent stability. This work provides a new perspective for rational construction and precise regulation for heteronuclear dual‐atom catalysts.

In-situ construction of ionic liquid salt-derived graphene-like dual-heteroatoms doping engineering as efficient metal-free electrocatalyst for oxygen reduction reaction

Metal-free heteroatom-doped carbon catalysts can effectively eliminate the degradation and pollution problems caused by metal dissolution. However, single heteroatom doping often restricts the regulation of geometric and electronic structures for oxygen reduction reaction (ORR) electrocatalysts. Herein, a dual atomic doping engineering to optimize the electronic structure and local coordination environment of ionic liquid salt-derived graphene-like host material as an efficient metal-free electrocatalyst for ORR. The resultant PNG catalyst with a typical nanosheets morphology with a high specific surface area and unique hierarchical porous structure. Benefiting from the uniform doping of P, N heteroatoms, graphene-like structure, optimized electronic structure and coordination environment, thus-prepared PNG-2 exhibits outstanding ORR activity, which the onset potential and half-potential are negatively shifted by around 70 mV and 46 mV, respectively, as compared to the commercial Pt/C (20 wt.%) for ORR. Furthermore, the PNG-2 exhibits the higher diffusion limiting current density, superior long-term stability as well as excellent resistance to methanol oxidation than Pt/C. Experimental studies and density functional theory (DFT) calculations reveal that the enhanced chemisorption of oxygen species (*OOH, *O and *OH) onto the P and N sites of the PNG catalysts can effectively accelerate the charge transfer kinetics and promote a favorable ORR performance.

Prussian Blue Analogues Derived Bimetallic CoNi@NC as Efficient Oxygen Reduction Reaction Catalyst for Mg‐Air Batteries

The magnesium‐air (Mg‐air) batteries are regarded as a highly promising system for electrochemical energy conversion and storage, owing to exceptional energy density, notable safety and eco‐friendliness. The development of high‐performance and durable non‐noble metal catalysts for the cathodic oxygen reduction reaction (ORR) is crucial for advancing the practical use of Mg‐air batteries. The synergistic interaction between different metals in bimetallic catalysts is an effective strategy for enhancing the activity and stability of the catalysts. Herein, various prussian blue analogues (PBA) were selected as precursors to synthesis the bimetallic CoNi@NC, monometallic Co@NC and Ni@NC catalysts due to tunable chemical compositions. Compared with Co@NC and Ni@NC, the bimetallic CoNi@NC pyrolyzed at 600°C (CoNi@NC‐600) exhibits outstanding ORR performances and stability in alkaline (0.1 M KOH) and neutral (3.5 wt% NaCl) electrolytes. Following 5000 CV cycles, the half‐wave potentials for CoNi@NC‐600 show only minor negative shifts of 8 and 7 mV, respectively. Meanwhile, the CoNi@NC‐600 possesses the similar ORR reaction mechanism and activity with Pt/C. The primary Mg‐air battery assembled with CoNi@NC‐600 displays better discharge performances than that of Co@NC and Ni@NC. This study lays the foundation for future investigations into the advancement of non‐precious bimetallic catalysts for ORR in Mg‐air batteries.

Mxene-based capacitive enzyme-free biofuel cell Self-Powered sensor for lead ion detection in human plasma

In response to the health risks posed by heavy metal lead, we have developed a self-powered sensor specifically designed for detection of lead ions in this work. This sensor is designed based on an enzyme-free biofuel cell as a self-powered source. The biofuel cell utilizes two-dimensional lamellar Au NPs-Ti3C2Tx heterostructures as the capacitive anode substrate material. The Ti3C2Tx MXene with the excellent charge storage capacity and fast discharge characteristics, provides a large instantaneous current for signal amplification. Furthermore, the DNA walker technique was combined to regulate the loading of ultra-small Au NPs exhibiting glucose oxidase-like properties. Meanwhile, Co, Mn nitrogen-doped carbon-based nanosheets were designed as the cathode with outstanding oxygen reduction reaction catalytic activity. As a result, the constructed enzyme-free biofuel cell has been used to detect Pb2+ with a wide linear range (0.01–7500 nM) and a low detection limit (0.43 pM). It has been successfully applied to the determination of Pb2+ in human plasma, achieving excellent recovery rates (94.0–110.5 %). The developed capacitive anodes not only significantly optimized the performance of the biofuel cell self-powered sensors, but also provided important insights for the future design and construction of biofuel cells.

Iron-Cobalt Phosphide Encapsulated in a N-Doped Carbon Framework as a Promising Low-Cost Oxygen Reduction Electrocatalyst for Zinc-Air Batteries.

The oxygen reduction reaction (ORR) plays a vital role in many next-generation electrochemical energy conversion and storage devices, motivating the search for low-cost ORR electrocatalysts possessing high activity and excellent durability. In this work, we demonstrate that iron-cobalt phosphide (FeCoP) nanoparticles encapsulated in a N-doped carbon framework (FeCoP@NC) represent a very promising catalyst for the ORR in alkaline media. The core-shell structured FeCoP@NC catalyst offered outstanding ORR activity with a half-wave potential (E1/2) of 0.86 V vs reversible hydrogen electrode (RHE) and excellent stability in a 0.1 M KOH electrolyte, outperforming commercial Pt/C and many recently reported noble-metal-free ORR electrocatalysts. The superiority of FeCoP@NC as an ORR electrocatalyst relative to Pt/C was further verified in prototype zinc-air batteries (ZABs), with the aqueous and flexible ZABs prepared using FeCoP@NC offering excellent stability, impressive open circuit voltages (1.56 and 1.44 V, respectively), and high maximum power densities (183.5 and 69.7 mW cm-2, respectively). Density functional theory calculations revealed that encapsulating FeCoP nanoparticles in N-doped carbon shells resulted in favorable electron penetration effects, which synergistically regulated the adsorption/desorption of ORR intermediates for optimal ORR performance while also boosting the electronic conductivity. Our findings offer valuable new insights for rational design of transition metal phosphide-based catalysts for the ORR and other electrochemical applications.

Coordination engineering of defective F and N co-doped carbon dots anchored silver nanoparticles for boosting oxygen reduction reaction

The carbon-based catalysts exhibit excellent electrocatalytic and stable performance toward oxygen reduction reaction (ORR), which are expected to replace expensive and scarce Pt-based catalysts. However, how to regulate the interaction between silver and carrier carbon dots (CD) to improve electrocatalytic performance toward oxygen reduction reaction (ORR) and stability, has not been systematically studied. In this study, we in-situ synthesized fluorine and nitrogen co-doped CD anchoring Ag nanoparticles by UV irradiation reduction method. The peak potential, onset-potential and half-wave potential of F, N-CD@Ag-0.1 are 0.85 V, 1.056 V, and 0.9 V, respectively, indicating outstanding ORR performance. The current density of F, N-CD@Ag-0.1 remains 97.5 % after 50, 000 s, showing more excellent stability than Pt/C. The impressive ORR catalytic activity and stability of F, N-CD@Ag-0.1 could be attributed to the strong anchoring effect of nitrogen-doped CD on Ag. This effect leads to a significant interaction and charge transfer between Ag and CD, thereby enhancing the charge transfer process during the catalytic reaction. This project aims to design a carbon dot/silver composite catalyst with high ORR catalytic performance and favorable stability. The implementation of this project provides good theoretical guidance for the design of carbon nanomaterial-based catalytic systems.

Electrocatalytic Oxygen Reduction Using Metastable Zirconium Suboxide

AbstractStrategies for discovery of high‐performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr−ZrO2 interfaces but does not appear in the experimental Zr−O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal‐based catalysts. Addition of Fe3C nanoparticles to give a Zr−Zr3O−Fe3C/NC catalyst (NC=nitrogen‐doped carbon) gives a half‐wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc‐air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm−2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high‐performance electrocatalysts.

Electrocatalytic Oxygen Reduction Using Metastable Zirconium Suboxide.

Strategies for discovery of high-performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr-ZrO2 interfaces but does not appear in the experimental Zr-O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal-based catalysts. Addition of Fe3C nanoparticles to give a Zr-Zr3O-Fe3C/NC catalyst (NC=nitrogen-doped carbon) gives a half-wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc-air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm-2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high-performance electrocatalysts.

Nitrogen-bridged Cu-Zn dual-atom cooperative interface sites for efficient oxygen reduction reaction in Zn-air battery

Developing nonprecious catalysts with excellent behaviors for oxygen reduction reaction (ORR) has assumed considerable importance, but remains an arduous issue. Herein, we demonstrate a Kirkendall effect-pyrolysis (KEP) strategy to construct N-bridged Cu-Zn dual-atom supported on hollow N-doped carbon (Cu-Zn DA/HNC) for ORR. The hollow structure of N-doped carbon facilitates mass transfer and exposes more actives. What’s more, the shared N atom between Cu and Zn atoms is beneficial to enhance their synergetic effect, creating an appropriately enhanced O* binding. The resulting Cu-Zn DA/HNC displays excellent ORR activity in an alkaline electrolyte, following a nearly four-electron pathway of ORR. Even employing Cu-Zn DA/HNC as the cathode in ZABs, Cu-Zn DA/HNC presents a long cycling life up to 910 h and robust low-temperature adaptability. The facile and straightforward fabrication plus the outstanding ORR performance of Cu-Zn DA/HNC endows its great potential as a significant candidate in practical applications of ZAB.

Self‐Adjustment of Intrinsic Reaction Intermediate on Atomically Dispersed Co2–N6 Binuclear Sites Achieving Boosted Electrocatalytic Oxygen Reduction Performance

AbstractIsolated dual‐atom catalysts (DACs) have sparked enormous research enthusiasm in new energy community due to their great potentials to substitute the state‐of‐the‐art Pt‐based catalysts. Nevertheless, explicitly unraveling the underlying catalytic mechanisms is of critical significance for performance enhancement, yet remains a huge challenge. Herein, the study reports a reliable hard template‐mediated strategy to accomplish the construction of atomically isolated binuclear Co2‐N6 sites stabilized by ultrathin hollow carbon nanospheres (abbreviated as Co2‐DAs@CHNSs). Systematic spectroscopy characterization and theoretic calculations uncover that the Co2‐N6 sites follow a self‐adjusting mechanism caused by the intrinsic OH intermediate. The involvement of the ‐OH energy‐level modifier is found to induce the electron redistribution and alternation of antibonding orbital fillings for the generated Co2‐N6‐OH site, leading to reduced potential‐determining step (PDS) energy barrier, and thus boosted intrinsic activity. Consequently, the well‐managed Co2‐DAs@CHNSs afford outstanding oxygen reduction reaction (ORR) activity with a half‐wave potential of 0.87 V in alkaline electrolyte, overmatching the Pt benchmark. Furthermore, the Co2‐DAs@CHNSs‐assembled aqueous and all‐solid‐state rechargeable zinc–air batteries (ZABs) demonstrate high power density, large specific capacity, and robust stability. The findings offer an innovative avenue to rationally manipulate the electronic structures of active sites for DACs via a powerful self‐ligand modification strategy.

Main Group SnN4O Single Sites with Optimized Charge Distribution for Boosting the Oxygen Reduction Reaction.

Transition metal single-atom catalysts (SACs) have been regarded as possible alternatives to platinum-based materials due to their satisfactory performance of the oxygen reduction reaction (ORR). By contrast, main-group metal elements are rarely studied due to their unfavorable surface and electronic states. Herein, a main-group Sn-based SAC with penta-coordinated and asymmetric first-shell ligands is reported as an efficient and robust ORR catalyst. The introduction of the vertical oxygen atom breaks the symmetric charge balance, modulating the binding strength to oxygen intermediates and decreasing the energy barrier for the ORR process. As expected, the prepared Sn SAC exhibits outstanding ORR activity with a high half-wave potential of 0.912 V (vs RHE) and an excellent mass activity of 13.1 A mgSn-1 at 0.850 V (vs RHE), which surpasses that of commercial Pt/C and most reported transition-metal-based SACs. Additionally, the reported Sn SAC shows excellent ORR stability due to the strong interaction between Sn sites and the carbon support with oxygen atom as the bridge. The excellent ORR performance of Sn SAC was also proven by both liquid- and solid-state zinc-air battery (ZAB) measurements, indicating its great potential in practical applications.

Fe-Co Co-Doped 1D@2D Carbon-Based Composite as an Efficient Catalyst for Zn-Air Batteries.

A Fe-Co dual-metal co-doped N containing the carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe1Co-HNC, which was formed with 1D carbon nanotubes and 2D carbon nanosheets including a rich mesoporous structure, exhibited outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm-2 with the Fe1Co-HNC catalyst. It also displayed superior performance in zinc-air batteries. This method provides a promising strategy for the fabrication of efficient transition metal-based carbon catalysts.