Photocatalytic Coupling of CH4 and CO2 to Ethanol on Asymmetric Ce-O-Zn Sites

Partial oxidation of methane (CH4) to value-added products is significantly challenging due to the highly inert chemical property of CH4 at ambient conditions and easy over-oxidation into carbon dioxide (CO2) or carbon monoxide (CO) at elevated temperatures and pressures. Targeting this challenge, the efficient photocatalytic coupling of CO2 and CH4 into ethanol is demonstrated, using a cerium (Ce)-doped zinc oxide (ZnO) photocatalyst with abundant Ce & horbar;O & horbar;Zn units. Under light illumination, CO2 is adsorbed on the Ce atoms and photo-reduced to CO, and CH4 is captured by the Zn atoms and photo-oxidized to hydroperoxymethane (CH3OOH). The close proximity of Ce and Zn atoms on the Ce & horbar;O & horbar;Zn units allowed to further efficiently couple the as-formed CO and CH3OOH into ethanol. Without additional Oxygen (O-2) oxidant or sacrificial regent, the ethanol production rate reached 580 mu mol g(-1) h(-1), substantially exceeding previously reports on photocatalytic CH4 oxidation. This work features to convert two greenhouse gases into value-added chemicals with adjacent and asymmetric reaction sites, suggesting attractive potentials for CH4 and CO2 utilization.