Solvothermally-Prepared Cu2O Electrocatalysts for CO2 Reduction with Tunable Selectivity by the Introduction of p-Block Elements

The electroreduction of CO2 to fuels and chemicals is an attractive strategy for the valorization of CO2 emissions. In this study, a Cu2O electrocatalyst prepared by a simple and potentially scalable solvothermal route effectively targeted CO evolution at low-to-moderate overpotentials [with a current efficiency for CO (CECO) of ca. 60% after 12h at -0.6V vs. reversible hydrogen electrode, RHE], and its selectivity was tuned by the introduction of p-block elements (In, Sn, Ga, Al) into the catalyst. SEM, HRTEM, and voltammetric analyses revealed that the Cu2O catalyst undergoes extensive surface restructuring (favorable for CO evolution) under the reaction conditions. The modification of Cu2O with Sn and In further enhanced the current efficiency (CE) for CO (ca. 75% after 12h at -0.6V). In contrast, the introduction of Al altered the selectivity profile of the catalyst significantly, decreasing the selectivity toward CO but promoting the reduction of CO2 to ethylene (CE approximate to 7%), n-propanol, and ethanol (CE approximate to 2% each) at -0.8V vs. RHE. This result is related to a decreased reducibility of Al-doped Cu2O that might preserve Cu+ species (favorable for C2H4 production) under the reaction conditions, which is supported by XRD, X-ray photoelectron spectroscopy, and H-2 temperature-programmed reduction observations.