Oxygen vacancy and facet engineering of cuprous oxide by doping transition metal oxides for boosting alcohols selectivity in electrochemical CO2 reduction

Nanostructured Cu-based catalysts have gained much attention for electrochemical CO2 reduction (ECR) to value-added alcohols, while they are facing the challenges of unsatisfactory catalytic activity and selectivity. Herein, oxygen vacancy and facet engineering strategies are employed to modulate the ECR performance of Cu2O by doping transition metal oxides (TMOs). TMOs doping improves CO2 conversion by suppressing hydrogen evolution reaction (HER). The catalyst doped with 0.001 mol% ZnO exhibits a high alcohols Faradaic efficiency of 63.67% at −0.3 V vs. RHE, which exceeds that of the bare Cu2O (35.4%). The enhanced activity and alcohols selectivity is ascribed to the enriched oxygen vacancy defects (57.26%) for enhanced CO2 adsorption and activation and the synergistic effect between Cu and Zn sites for facilitated CO* protonation and C–C coupling. Alcohols selectivity increases from 56.87% to 64.27% and then declines to 63.67% with the increasing ZnO molar ratio from 0.00025 to 0.001. The Cu2O–ZnO-0.0005 catalyst features the octahedral structure (enclosed by the (111) and (100) facets) exhibits favorable ECR performance with the highest alcohols selectivity of 64.27% at −0.3 V vs. RHE. The enhanced alcohols selectivity is associated with the facet-dependent effect, as the exposed (111) facet favors CO2 adsorption and activation in ECR.