Chlorine anion stabilized Cu2O/ZnO photocathode for selective CO2 reduction to CH4

Although Cu 2 O-based material is one of the most promising catalysts, the deactivation of surface severely limits its selectivity and stablity. Here, we present a chlorine (Cl)-modified Cu 2 O/ZnO heterostructure (CCZO) as photocathode with remarkable CH 4 faradaic efficiency (88.6%) and durability (over 5 h). The Cl ions in CCZO serve as a passivator to stabilize Cu 2 O against photo-corrosion. Stabilized Cu + active sites promote the hydrogenation of *CO intermediate, which provides a strong driving force for CO 2 reduction to CH 4 . Calculation results indicate that for CCZO the hydrogenation of *CO trends to form *CHO (energy barrier of 0.220 eV) rather than CO (0.344 eV), further confirming the high selectivity of CCZO to CH 4 . This work sheds insight on the catalytic mechanism of CCZO to modulate the energy barrier of intermediate *CO combined with H + , providing a new idea to develop high selectivity and stable catalysts for CO 2 reduction. • The Cl-modified Cu 2 O/ZnO (CCZO) heterostructure as photocathode exhibits outperformance of CO 2 reduction to CH 4 with the highest FE CH4 of 88.6% at -0.3 V vs. RHE. • Cl ions over Cu 2 O surface contributes to the stabilization of the Cu + active site, which provides a strong driving force for the conversion of CO 2 to CH 4 .