Regulating the d-band electrons of the Fe-N-C single-atom catalyst for high-efficiency CO 2 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 2 electroreduction reaction (CO 2 RR) but suffers from insufficient intrinsic activity and inferior conductivity, which could be addressed by redistributing the electron density via heteroatom doping. Herein, we synthesized S-doped Fe-N-C (Fe-SN-C) as an advanced electrocatalyst for CO 2 RR 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 CO 2 RR 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 -2 at -0.8 V for 2e - CO 2 RR. This finding provides a feasible and controllable method to achieve advanced electrocatalysts for efficient energy conversion.