Enhanced methanol selectivity of CuxO/TiO2 photocatalytic CO2 reduction: Synergistic mechanism of surface hydroxyl and low-valence copper species. (January 2022) - Xi, Hanchen
Highlights: CO2 photoreduction to methanol on Cu/Ti(H2 ) was 17-fold higher than Cu/Ti(air). Oxygen vacancies on Cu/Ti(H2 ) led to more hydroxyl protons and photo-electrons. Low-valence copper species promoted CO2 and intermediates adsorption/activation. Synergistic effects of surface hydroxyl and low-valence copper were proposed. Abstract: Photocatalytic CO2 reduction to methanol is a promising method to solve the energy and environmental issues. Herein, copper species with different valences loading on TiO2 via the oxidizing and reducing atmosphere treatment, denoted as Cu/Ti(air) and Cu/Ti(H2 ), for CO2 photoreduction. The methanol yield greatly increased on Cu/Ti(H2 ) with low-valence copper species, which was 17-fold higher than that of Cu/Ti(air). It showed that the reducing atmosphere generated Ti 3+ species and oxygen vacancies on Cu/Ti(H2 ), leading to richer protons of surface hydroxyls adsorbed on surface and available photo-electrons. In addition, in-situ CO2 adsorption-DRIFTS suggested that low-valence copper species of Cu/Ti(H2 ) had better ability of CO2 activation and CO*, HOCO −, HCOOH active intermediates adsorption, which further hydrogenated and conversed to CH3 OH, with the help of protons and photo-electrons. Therefore, owing to the synergistic effects of surface hydroxyl and low-valence copper species, Cu/Ti(H2 ) was provided with the superior conversion and selectivity of CO2 to methanol.