A Sulfur-Doped Copper Catalyst with Efficient Electrocatalytic Formate Generation during the Electrochemical Carbon Dioxide Reduction Reaction

Catalysts involving post-transition metals have shown almost invincible performance on generating formate in electrochemical CO₂ reduction reaction (CO₂RR). Conversely, Cu without post-transition metals has struggled to achieve comparable activity. In this study, a sulfur (S)-doped-copper (Cu)-based catalyst is developed, exhibiting excellent performance in formate generation with a maximum Faradaic efficiency of 92 % and a partial current density of 321 mA cm⁻². Ex situ structural elucidations reveal the presence of abundant grain boundaries and high retention of S−S bonds from the covellite phase during CO₂RR. Furthermore, thermodynamic calculations demonstrate that S−S bonds can moderate the binding energies with various intermediates, further improving the activity of the formate pathway. This work is significant in modifying a low-cost catalyst (Cu) with a non-metallic element (S) to achieve comparable performance to mainstream catalysts for formate generation in industrial grade.