Bio-inspired engineering of Bi₂S₃-PPy composite for the efficient electrocatalytic reduction of carbon dioxide

Using surface-engineered chemical composites to enhance the binding energy of reaction intermediates and the conductivity is an attractive route to achieve a high partial current density and increased yield of the target products. Herein, conductive polymer polypyrrole (PPy) was used to regulate the electronic structure of Bi2S3 and facilitate the activation of CO2 molecules to enhance the CO2 electroreduction activity. The constructed electrocatalyst with a unique 3D hierarchical urchin-like nanoflower morphology was composed of Bi2S3 nanowire assemblies with rich S vacancies via PPy modification, featuring an improved electron-transfer ability and outstanding formate faradaic efficiency of 91.18% and partial current density of -56.95 mA cm(-2), as well as good stability at a moderate potential in an H-type cell. More importantly, it could deliver current densities exceeding -300 mA cm(-2) without compromising the selectivity of formate in a flow-cell reactor. A possible reaction mechanism for formate formation related to HCO3- was proposed based on the in situ ATR-IR spectra, which could bring a new scientific understanding of CO2 reduction. DFT calculations further demonstrated that the optimized electronic structure, boosted adsorption and activation of CO2, and protonation process contributed to a reduced formation energy for the formate intermediate *OCHO, leading to the enhanced performance. More impressively, Zn-CO2 batteries equipped with Bi2S3-PPy displayed a maximum power density of 2.4 mW cm(-2) and a superior cycle stability of >110 h. This study underlines the effectiveness of designing composite electrocatalysts to improve the CO2RR performance and thus provides a viable path toward carbon neutrality.