CO2 photoelectroreduction with enhanced ethanol selectivity by high valence rhenium-doped copper oxide composite catalysts.

CuO supported catalyst with high valence rhenium doping were specially studied for photoelectrocatalytic reduction of CO2 to small molecular alcohols, which were synthesized by nitrate thermal decomposition method on anatase TiO2 nanotube arrays (TiO2-NTs). Photoelectrochemical measurements indicate that the high valence rhenium doping helps in improving the catalytic activity and selectivity of CuO supported catalysts. For the case of 6 wt% Re-doped CuO/TiO2-NTs calcined at 723 K, the principal products are methanol and ethanol with yield up to 19.9 μmol and 7.5 μmol after 5 h photoelectrocatalysis at external potential of -0.4 V under simulated solar illumination. In contrast, the products catalyzed by undoped CuO/TiO2-NTs are only methanol and formaldehyde. These results indicate that the high valence rhenium doping will promote the alcoholization process and benefit the CC coupling, leading to the selective conversion of CO2 to ethanol. Furthermore, under suitable external potential (-0.5 V) the CO2 conversion product is almost entirely composed of ethanol.