Cu7S4 nanosheets enriched with Cu–S bond for highly active and selective CO2 electroreduction to formate

Abstract

Cu has been regarded as the most promising catalyst for electrochemical CO₂ reduction reaction (CO₂RR), a promising strategy for reducing CO₂ emission and converting CO₂ to value-added chemicals using renewable electrical energy. Nevertheless, selective formate (HCOO⁻) production via CO₂RR over Cu-based catalysts has been rarely reported because Cu is generally used as the active site for C–C coupling to C₂₊ products. Herein, we demonstrate that Cu₇S₄ nanosheets (NSs) can serve as efficient catalysts for CO₂RR to HCOO⁻. Detailed investigations show that, different from CuO that enables the C–C coupling to C₂₊ products, the Cu–S bond in Cu₇S₄ NSs favors protonation to produce HCOO⁻. Impressively, Cu₇S₄ NSs display a HCOO⁻ faradaic efficiency (FE) of 82.7% with a formation rate of 8.5 mmol h⁻¹ cm⁻², which has surpassed most reported catalysts for CO₂RR to HCOO⁻. This work provides a highly efficient catalyst for CO₂RR to HCOO⁻, which may promote fundamental research on the catalyst design for CO₂RR to target products.