Fig. 1. Electrochemical CO₂ reduction on various metal sulfides in 0.1 M NaCl saturated with 1 atm CO₂ at room temperature (~25°C).

(A and B) FEs for CO₂ reduction to (A) CO (CO₂ + 2H⁺ + 2e^– → CO + H₂O) and (B) HCOO^– (CO₂ + 2H⁺ + 2e^– → HCOO^–) at –0.8, –1.0, and –1.2 V versus the SHE. (C) CO production efficiencies on CdS and Ag₂S as a function of electric potential. Error bars correspond to the overall reproducibility of the experimental data that was evaluated from three independent experiments.