Achieving Efficient CO₂ Electrolysis to CO by Local Coordination Manipulation of Nickel Single-Atom Catalysts

Selective electroreduction of CO₂ to C₁ feed gas provides an attractive avenue to store intermittent renewable energy. However, most of the CO₂-to-CO catalysts are designed from the perspective of structural reconstruction, and it is challenging to precisely design a meaningful confining microenvironment for active sites on the support. Herein, we report a local sulfur doping method to precisely tune the electronic structure of an isolated asymmetric nickel-nitrogen-sulfur motif (Ni₁-NSC). Our Ni₁-NSC catalyst presents >99% faradaic efficiency for CO₂-to-CO under a high current density of -320 mA cm^-2. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and differential electrochemical mass spectrometry indicated that the asymmetric sites show a significantly weaker binding strength of *CO and a lower kinetic overpotential for CO₂-to-CO. Further theoretical analysis revealed that the enhanced CO₂ reduction reaction performance of Ni₁-NSC was mainly due to the effectively decreased intermediate activation energy.