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Atomically dispersed metal‐nitrogen‐carbon (M‐N‐C) catalysts have exhibited encouraging oxygen reduction reaction (ORR) activity. Nevertheless, the insufficient long‐term stability remains a widespread concern owing to the inevitable 2‐electron byproducts, H2O2. Here, we construct Co‐N‐Cr cross‐interfacial electron bridges (CIEBs) via the interfacial electronic coupling between Cr2O3 and Co‐N‐C, breaking the activity‐stability trade‐off. The partially occupied Cr 3d‐orbitals of Co‐N‐Cr CIEBs induce the electron rearrangement of CoN4 sites, lowering the Co‐OOH* antibonding orbital occupancy and accelerating the adsorption of intermediates. Consequently, the Co‐N‐Cr CIEBs suppress the two‐electron ORR process and approach the apex of Sabatier volcano plot for four‐electron pathway simultaneously. As a proof‐of‐concept, the Co‐N‐Cr CIEBs is synthesized by the molten salt template method, exhibiting dominant 4‐electron selectively and extremely low H2O2 yield confirmed by Damjanovic kinetic analysis. The Co‐N‐Cr CIEBs demonstrates impressive bifunctional oxygen catalytic activity (▵E=0.70 V) and breakthrough durability including 100 % current retention after 10 h continuous operation and cycling performance over 1500 h for Zn‐air battery. The hybrid interfacial configuration and the understanding of the electronic coupling mechanism reported here could shed new light on the design of superdurable M‐N‐C catalysts. [ABSTRACT FROM AUTHOR]

Cobalt–nitrogen–carbon is hitherto considered as one of the most satisfactory alternatives to precious metal catalysts for oxygen electrocatalysts. However, precisely tuning the local coordination of Co sites and thus engineering d‐orbital electron configuration to optimize the binding energy of the intermediates remains a huge challenge. Herein, a robust electrostatic self‐assembly strategy is developed to engineer penta‐coordinated Co sites by introducing axial O ligands with atomic‐level precision to form CoN4O1 configurations on MXene nanosheets (CoN4‐O/MX). The optimized CoN4‐O/MX demonstrates outstanding bifunctional electrocatalytic performance with a small potential gap of 0.72 V, significantly outperforming the cobalt–nitrogen–carbon catalyst with plane‐symmetric CoN4 sites and precious metal counterparts. The Zn–air batteries integrated with CoN4‐O/MX provide an outstanding peak power density of 182.8 mW cm−2 and a long‐term cyclability for 250 h. Density functional theory calculations reveal that CoO coordination induces electronic delocalization to draw off partial electrons from the dz2 orbital, which forms unsaturated orbital filling and lifts the energy level, resulting in a stronger Lewis basicity to facilitate electron injection into the intermediate. The study presented here provides not only a novel methodology to achieve precise control of heteroatom coordination, but also a fundamental understanding about the structure–activity relationships of dz2 orbitals. [ABSTRACT FROM AUTHOR]

Atomically dispersed Fe–N–C catalysts have been extensively deemed as appealing substitutes for Pt-series catalysts towards oxygen reduction reactions (ORRs). Nevertheless, most reported Fe–N–C materials suffer from inefficient Fe-based nanoparticles and low-density Fe–Nx sites. Herein, a Zn/g-C3N4-mediated dual-template strategy was employed to synthesize densely populated atomic Fe–Nx center-embedded N-doped carbon nanosheets (SAs-Fe/N-CNSs) with adjustable porous structures by the simple pyrolysis of D -glucosamine/FeZn/g-C3N4 complexes. g-C3N4 works as a structure-guiding 2D template and offers abundant coordination-N trapping sites for anchoring Fe atoms, simultaneously. ZnCl2 serves as a self-sacrificial template creating a hierarchical porous structure by its volatilization as well as hinders the agglomeration of Fe atoms by spatial segregation during pyrolysis. Due to the high-density atomic Fe–Nx moieties, unique 2D structure, hierarchical porosity, and large surface area, the optimal SAs-Fe/N-CNS catalyst exhibits satisfying ORR performance including excellent activity (E1/2 = 0.91 V) and desirable durability, surpassing the Pt/C catalyst. Additionally, the superb performance of SAs-Fe/N-CNS-based Zn–air batteries with a maximum power density of 157.03 mW cm−2 verifies their promising application in practical electrochemical systems. [ABSTRACT FROM AUTHOR]

Fe-N-C catalyst for oxygen reduction reaction (ORR) has been considered as the most promising nonprecious metal catalyst due to its comparable catalytic performance to Pt in proton exchange membrane fuel cells (PEMFCs). The active centers of Fe-pyrrolic N 4 have been proven to be extremely active for ORR. However, forming a stable Fe-pyrrolic N 4 structure is a huge challenge. Here, a Cyan-Fe-N-C catalyst with Fe-pyrrolic N 4 as the intrinsic active center is constructed with the help of axial Fe 4 C atomic clusters, which shows a half-wave potential of up to 0.836 V (vs. RHE) in the acid environment. More remarkably, it delivers a high power density of 870 and 478 mW cm -2 at 1.0 bar in H 2 -O 2 and H 2 -Air fuel cells, respectively. According to theoretical calculation and in situ spectroscopy, the axial Fe 4 C can provide strong electronic perturbation to Fe-N 4 active centers, leading to the d-orbital electron delocalization of Fe and forming the Fe-pyrrolic N 4 bond with high charge distribution, which stabilizes the Fe-pyrrolic N 4 structure and optimizes the OH* adsorption during the catalytic process. This work proposes a new strategy to adjust the electronic structure of single-atom catalysts based on the strong interaction between single atoms and atomic clusters., (© 2023 Wiley-VCH GmbH.)

Heterostructures show great potential in energy storage due to their multipurpose structures and function. Recently, two-dimensional (2D) graphene has been widely regarded as an excellent substrate for active materials due to its large specific surface area and superior electrical conductivity. However, it is prone to self-aggregation during charging and discharging, which limits its electrochemical performance. To address the graphene agglomeration problem, we interspersed polypyrrole carbon nanotubes between the graphene cavities and designed three-dimensional (3D)-heterostructures of ZnMn 2 O 4 @rGO-polypyrrole carbon nanotubes (ZMO@G-PNTs), which demonstrated a high rate and cyclic stability in lithium-ion capacitors (LICs). Furthermore, the 3D porous structure provided more surface capacity contribution than 2D graphene, ultimately resulting in a better stability (333 mAh g -1 after 1000 cycles at 1 A g -1 ) and high rate capacity (208 mAh g -1 at 5 A g -1 ). Also, the mechanism of performance difference between ZMO@G-PNTs and ZMO@G was investigated in detail. Moreover, LICs built from ZMO@G-PNTs as an anode and activated carbon as a cathode showed an energy density of 149.3 Wh kg -1 and a power density of 15 kW kg -1 and cycling stability with a capacity retention of 61.5% after 9000 cycles.