From local coordination to microenvironment: Synergistic promotion of CO₂ reduction reaction on a sulfur-modulated...

Unraveling the reaction mechanism of the electrochemical CO₂ reduction reaction (CO₂RR) is a cornerstone in the quest for high-performance catalysts. This work adopts S-doped NiN₄ (NiN₃S₁) as a probe to reveal the synergistic promotion of local coordination and the reaction microenvironment on CO₂RR. The results show that N, S-coordination decreases the required potential for CO₂ chemical adsorption from -0.54 to -0.23 V. An explicit water-assisted mechanism for CO₂ activation is demonstrated, where H₂O molecules act as proton donors and form hydrogen-bond networks to facilitate CO₂ activation and reduce the reaction energy for *COOH formation. The applied potential (U) vs. Standard Hydrogen Electrode (SHE) promotes electron transfer and proton-coupled processes, thus improving the intermediate adsorption and reaction activity. As a result, the limiting potential of CO₂RR to CO decreases from -1.38 to -0.48 V with the increase in applied potential (U) vs. SHE from 0 to -0.84 V. Hydrogen evolution reaction on NiN₃S₁ is investigated as well to reflect the high CO₂RR selectivity. The results of this work highlight the synergistic promotion of coordination environment, explicit water molecules, and applied potential (U) vs. SHE to efficient CO₂RR, providing theoretical guidance for designing advanced CO₂RR electrocatalysts.