CO 2 Reduction of Hybrid Cu 2 O–Cu/Gas Diffusion Layer Electrodes and their Integration in a Cu‐based Photoelectrocatalytic Cell

Cu 2 O/gas diffusion layer (GDL) electrodes prepared by electrodeposition were studied for the electrocatalytic reduction of CO 2 . The designed electrode was also tested in solar‐light‐induced CO 2 conversion in combination with a CuO/NtTiO 2 photoanode using a compact photoelectrocatalytic (PEC) cell. Both PEC cell electrodes were prepared using non‐critical raw materials and low cost, easily scalable procedures. In the PEC experiments, a total carbon faradaic selectivity of about 90 % to formate and about 75 % to acetate was obtained after 24 h of operations without application of potential/current or using sacrificial agents. In electrocatalytic tests of CO 2 reduction at −1.5 V, the same electrode yielded high total faradaic selectivity (>95 %) but formed selectively formate (about 80 % selectivity) rather than acetate. The in situ transformation of the Cu 2 O/GDL electrode leads to the formation of a hybrid Cu 2 O–Cu/GDL system. Cyclic voltammetry data indicate that the potential and the presence of CO 2 (not only of HCO 3 − species) are both important elements in this transformation. Data also indicate that the surface concentration of CO 2 (or of its products of transformation) on the electrode is an important factor to determine performance in the conversion of CO 2 .