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

Abstract

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.