Bi19Br3S27 nanorods for formate production from CO2 electroreduction with high efficiency and selectivity

Electrocatalytic CO2 reduction by renewable electricity is a promising approach to mitigate greenhouse effect and energy crisis, whereas the product selectivity and efficiency of catalysts remain to be significantly improved. Adjusting the electronic structure of catalysts by modulating the coordination environment of active sites is an effective way to improve their catalytic performance, but it is limited to deliberate doping. Herein, we synthesize Bi19Br3S27 nanorod as an electrocatalyst for CO2 reduction and realize the electronic structure modulation of Bi sites by S and Br comodification via an in-situ reconstruction. The as-obtained catalyst shows high Faradaic efficiency of formate (FEformate) of 98% at −1.1 V versus reversible hydrogen electrode (vs. RHE) and above 96% in a wide potential range of ∼ 700 mV (-1.1 V ∼ -1.8 V vs. RHE), superior to most of the reported catalysts. Meanwhile, a current density of about 150 mA cm−2 has been achieved in a flow cell with FEformate of 90%. It is disclosed that Bi19Br3S27 has been reconstructed to S,Br-comodified Bi during CO2 reduction process, resulting in positively charged Bi sites, which enhance the stability of CO2*- and HCOO*- intermediates and improve the catalytic activity towards formate formation. Compared with S-modified Bi and pure Bi, the S,Br-comodified Bi shows enhanced electron transfer rate and reaction kinetics, favoring its high efficiency in CO2RR. Ultimately, a maximum solar-to-formate conversion efficiency of ∼ 4.75% has been achieved in an electrolyzer integrating CO2RR and OER (O2 evolution reaction) powered by Si solar cells.