Si-doping induced electronic structure regulation of single-atom Fe sites for boosted CO2 electroreduction at low overpotentials

Transition metal-based single-atom catalysts (TM-SACs) are promising alternatives to Au-and Ag-based electrocatalysts for CO production through CO2 reduction reaction. However, developing TM-SACs with high activity and selectivity at low overpotentials is challenging. Herein, a novel Fe-based SAC with Si doping (Fe-N-C-Si) was prepared, which shows a record-high electrocatalytic performance toward the CO2-to-CO conversion with exceptional current density (> 350.0 mA cm(-2)) and similar to 100% Faradaic efficiency (FE) at the overpotentials of < 400 mV, far superior to the reported Fe-based SACs. Further assembling Fe-N-C-Si as the cathode in a rechargeable Zn-CO2 battery delivers an outstanding performance with a maximal power density of 2.44 mW cm(-2) at the output voltage of 0.30 V, as well as the high cycling stability and FE (> 90%) for CO production. Experimental combined with theoretical analysis unraveled that the nearby Si dopants in the form of Si-C/N bonds modulates the electronic structure of the atomic Fe sites in Fe-N-C-Si to significantly accelerate the key pathway involving *CO intermediate desorption, inhibiting the poisoning of the Fe sites under high CO coverage and thus boosting the CO2RR performance. This work provides an efficient strategy to tune the adsorption/desorption behaviors of intermediates on single-atom sites to improve their electrocatalytic performance.

Automated summary

A novel Si-doped Fe-based single-atom catalyst (Fe-N-C-Si) with exceptional electrocatalytic performance for CO2-to-CO conversion has been successfully prepared. The Fe-N-C-Si catalyst exhibits high current density (> 350.0 mA cm(-2)) and Faradaic efficiency (FE) close to 100% at overpotentials of less than 400 mV, surpassing previously reported Fe-based SACs. Moreover, when used as the cathode in a rechargeable Zn-CO2 battery, Fe-N-C-Si demonstrates outstanding power density, cycling stability, and FE (> 90%) for CO production.