Regulating the d-band electrons of the Fe-N-C single-atom catalyst for high-efficiency CO electroreduction by electron-donating S-doping.

Developing highly efficient electrocatalysts is crucially significant for the application of advanced energy conversion. The Fe-N-C single-atom catalyst is promising for CO electroreduction reaction (CORR) but suffers from insufficient intrinsic activity and inferior conductivity, which could be addressed by redistributing the electron density heteroatom doping. Herein, we synthesized S-doped Fe-N-C (Fe-SN-C) as an advanced electrocatalyst for CORR using a simple trapping-pyrolysis strategy. Density functional theory calculations and experimental results indicate that S doping increases the d-band electrons and conductivity of Fe-SN-C by electron donating, and thus boosts *CO desorption during the CORR process and suppresses the competing hydrogen evolution reaction. Consequently, Fe-SN-C exhibits the maximum CO faradaic efficiency of 93% at -0.5 V and the highest partial current density of 10.1 mA cm at -0.8 V for 2e CORR. This finding provides a feasible and controllable method to achieve advanced electrocatalysts for efficient energy conversion.