Nitrogen imported in nickel clusters promotes carbon dioxide electrochemical reduction to carbon monoxide

The Ni-N coordination structure has been shown to be conducive to the electrochemical CO 2 reduction reaction (CO 2 RR) to CO, and this process has been extensively validated. However, the impact of Ni-N coordination structures within Ni-based clusters on CO 2 RR has received relatively limited research attention to date. In this study, catalysts containing Ni single atoms and Ni n clusters (Ni-N/Ni n ) were synthesised, and subsequently, Ni n clusters were transformed into Ni n N x clusters (Ni-N/Ni n N x ) through secondary nitridation. The experimental results, as illustrated by X-ray photoelectron spectra and X-ray absorption fine structure spectra, demonstrate that the Ni-N bond in Ni-N/Ni n N x increased and Ni- N -Ni bonds within atomic clusters were generated, thereby confirming the transformation from Ni n clusters to Ni n N x clusters. Density functional theory calculations show that the Ni n N x clusters have a lower energy barrier for the *CO 2 −  + H +  → *COOH step compared to Ni n clusters, and promote the entire reaction. Furthermore, in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) calculations collectively indicate that abundant Ni-N coordination structures in clusters effectively reduce the energy barrier of CO 2  + e −  → *CO 2 − and facilitate the activation of CO 2 to *CO 2 − across a broader potential window. Ni-N/Ni n N x demonstrates high Faraday efficiency of CO (FE COmax  = 98.6 % at −0.4 V vs. RHE), a wider potential window (−0.3 to −0.8 V vs. RHE, FE CO  > 90 %) and high CO partial current density (j CO  > 100 mA cm −2 ). In comparison with Ni-N/Ni n , the maximum CO partial current density of Ni-N/Ni n N x is enhanced by approximately 4.6 times. These findings offer valuable insights into the structure–activity relationship of Ni-based cluster catalysts and facilitate the development of more advanced atomically cluster catalysts.