Reduction of CO 2 on n ‐ GaAs Electrodes and Selective Methanol Synthesis

Faradaic efficiencies and current voltage characteristics for the reduction of to on (111 As) single‐crystal electrodes have been determined. The yield of is ∼ 100% for current densities of ∼ 140 μA/cm 2 at −1.2 to −1.4V vs. SCE. The excess current due to was found to have a threshold at and a maximum at . The current also exhibited a rotation‐independent j/v characteristic that is interpreted as a rate‐determining surface chemical combination step involving adsorbed H atoms and a carbon containing intermediate. The p H dependence of the saturation current is modeled with a kinetic scheme involving the parallel reduction of H + and .