Atomically dispersed Ni–Nx species anchored porous carbon matrix with embedded Ni nanoparticles was synthesized for highly efficient hydrogen evolution in alkaline conditions.

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Emerging single‐atom catalysts (SACs) hold great promise for CO2 electroreduction (CO2ER), but the design of highly active and cost‐efficient SACs is still challenging. Herein, a gas diffusion strategy, along with one‐step thermal activation, for fabricating N‐doped porous carbon polyhedrons with trace isolated Fe atoms (Fe1NC) is developed. The optimized Fe1NC/S1‐1000 with atomic Fe‐N3 sites supported by N‐doped graphitic carbons exhibits superior CO2ER performance with the CO Faradaic efficiency up to 96% at −0.5 V, turnover frequency of 2225 h−1, and outstanding stability, outperforming almost all previously reported SACs based on N‐doped carbon supported nonprecious metals. The observed excellent CO2ER performance is attributed to the greatly enhanced accessibility and intrinsic activity of active centers due to the increased electrochemical surface area through size modulation and the redistribution of doped N species by thermal activation. Experimental observations and theoretical calculations reveal that the Fe‐N3 sites possess balanced adsorption energies of *COOH and *CO intermediates, facilitating CO formation. A universal gas diffusion strategy is used to exclusively yield a series of dimension‐controlled carbon‐supported SACs with single Fe atoms while a rechargeable Zn–CO2 battery with Fe1NC/S1‐1000 as cathode is developed to deliver a maximal power density of 0.6 mW cm−2.

Development of inexpensive and efficient oxygen evolution reaction (OER)catalysts in acidic environment is very challenging, but important for practical proton exchange membrane (PEM) water electrolyzers. Here we develop a molecular iron-nitrogen coordinated carbon nanofiber supported on electrochemically exfoliated graphene (FeN 4 /NF/EG) electrocatalyst through carbonizing the precursor composed of iron ions absorbed on polyaniline-electrodeposited EG. Benefitting from the unique 3D structure, the FeN 4 /NF/EG hybrid exhibits a low overpotential of ~294 mV at 10 mA cm -2 for the OER in This article is protected by copyright. All rights reserved. 5precursor was uniformly electrodeposited on EG surface that was constructed by electrochemical exfoliation of graphite (Figure S1). After soaking in iron nitrate solution, carbonization, and acid etching treatments, the precursor was in situ converted into FeN x /NF/EG catalyst, which is supported by Fourier-transform infrared spectroscopy (FTIR) results (Figure S2). We systematically explored the influence of annealing at different temperatures (800-1000 o C) affecting the OER activity. The optimized carbonization temperature was 900 o C (FeN x /NF/EG), which exhibited the best electrocatalytic performance for OER in acid (Figure S3-S4). Moreover, this synthesis method can be further This article is protected by copyright. All rights reserved. 13 support from U.S. DOE fuel cell technologies Offices. M. Qiu thanks the support of Self-determined Research Funds of CCNU from Colleges' Basic Research and Operation of MOE ( 23020205170456). This research was supported by Dr. Y. Hu (Yongfeng Hu) to provide valuable discussion about the XAS analysis.Received: ((will be filled by the editorial staff))Revised: ((will be filled by the editorial staff))

Single atom catalysts (SACs) are considered as the emerging catalysts for boosting electricity‐driven CO2 reduction reaction (CRR) and hydrogen evolution reaction (HER). To replace the rare and expensive noble metal electrocatalysts, developing nonprecious metal SACs (NPMSACs) with superior electrocatalytic activity and stability is of paramount importance for achieving high efficiency in CRR and HER. Herein, a brief overview of recent achievements in the carbon‐rich NPMSACs for both CRR and HER is provided. The synthesis strategies and corresponding electrocatalytic performances of various carbon‐rich NPMSACs are discussed in the order of various metals (Ni, Co, Fe, Zn, and Sn for CRR, as well as Ni, Co, Fe, Mo, and W for HER), with a special attention paid to understand the structure–activity relationships. Finally, the remaining challenges and future perspectives for enhancing CRR and HER performance of NPMSACs are outlined.