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

Using surface-engineered chemical composites to enhance the binding energy of reaction intermediates and conductivity is an attractive route to achieve high partial current density and increased yield of 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 activity of CO2 electroreduction. The constructed electrocatalyst with unique 3D hierarchical urchin-like nanoflower morphology is composed of Bi2S3 nanowires assemblies with rich S vacancies via PPy modification, featuring improved electron transfer ability and achieving 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 can deliver current densities that exceed ‒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 demonstrate that the optimized electronic structure, boosted adsorption and activation of CO2, and protonation process contributes to a reduced formation energy for the formate intermediate *OCHO, leading to 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 >110 hours. This work underlines the effectiveness of designing composite electrocatalysts to improve CO2RR performance and thus provides a viable path to carbon neutrality.