Real-Time Mimicking the Electronic Structure of N-Coordinated Ni Single Atoms: NiS-Enabled Electrochemical Reduction of CO₂ to CO

N-coordinated Ni single atom (Ni–NC) is one of the best catalysts for the CO₂ reduction reaction (CO₂RR) to produce CO. However, no bulk Ni materials have exhibited high catalytic activity for CO₂RR. Herein, it is shown that NiS nanoparticles mimicking the electronic structure of Ni–NC in real-time enhance the CO₂RR activity in a zero-gap electrolyzer. In situ/Operando X-ray absorption spectroscopy suggests that under a cathodic potential, the electronic structure of NiS changes similarly to that of Ni–NC and modulated O_x–zS_y ligands with similar properties to Ni ligands, resulting in a mimicked electronic structure. However, NiS exhibits low stability owing to the loss of S species, key to mimicking N ligands. The future challenges in finding a stable mimicked electronic structure are discussed. Moreover, this work provides new insights into the development of catalysts from materials that have not generally been considered previously.