Copper vulcanization realizes selective carbon dioxide reduction to formate.

Herein, we demonstrate that the vulcanization of copper nanosheets (Cu 2 S NSs) can realize selective electrochemical carbon dioxide reduction (CO 2 RR) to formate (HCOOH). Results from experiments and in situ infrared spectroscopy reveal that Cu 2 S NSs favor CO 2 reduction along the HCOO* pathway, leading to the selective formation of HCOOH. Impressively, the Faraday efficiency (FE) of HCOOH surpasses 70% in a broad potential range from -0.84 to -1.21 V versus ( vs. ) reversible hydrogen electrode (RHE), with a maximum value of 82%.