Hierarchical Bi/S-modified Cu/brass mesh used as structured highly performance catalyst for CO2 electroreduction to formate

Electrocatalytic CO2 reduction reaction (ECO2RR) converts CO2 to high-value chemical products and promotes the carbon cycle. Sulfur (S)-modified copper (Cu) and bismuth (Bi)-based catalysts have been recognized as promising catalysts for ECO2RR. Both of them are highly active for selective formate generation, however, their poor stability and severe competing hydrogen evolution reaction (HER) remain challenging. Herein, S-doped Cu coated with Bi (Bi/Cu-S) is developed to improve ECO2RR selectivity to formate. Bi/Cu-S/brass mesh (BM) electrode material for ECO2RR was prepared by electrodepositing Bi on the surface of Cu-S/BM nanowires obtained from CuS/BM after the electroreduction. The Faradaic efficiency (FE) of the formate reaches the maximum of 94.3% at −0.9 V vs. reversible hydrogen electrode (RHE) with a partial current density as high as −50.7 mAcm−2 and a yield of 30.7 mmolh−1cm−2 under 0.5 M KHCO3 electrolyte. Meanwhile, the FE of formate is higher than 90% in the voltage range of −0.8 to −1.0 V vs. RHE. It also shows good stability at −0.9 V vs. RHE with the FE of formate remaining above 93% after a 10 h reaction. Density functional theory (DFT) calculations demonstrate that the Bi/Cu-S structure promotes the adsorption of CO2 and effectively inhibits HER by enhancing the adsorption of *H to a great extent, improving the selective conversion of CO2 to formate. This work deepens the understanding of the mechanism of Cu-Bi-based catalysts and S-modified Cu-based catalysts in selective ECO2RR to formate, and also provides a new strategy for catalyst design.