Study on photoelectrochemical CO2 reduction over Cu2O

Cu 2 O is an attractive photocathode for CO 2 reduction reaction (CO 2 RR). The instability of Cu 2 O usually makes it present as a part of composite or multilayer in CO 2 RR. The systematic study of pure Cu 2 O for CO 2 RR is quite rare, resulting in the elusiveness of the origin for the activity and selectivity of CO 2 RR under different conditions. Herein, exploration of the factors that influence the product distribution and Faradic efficiency of CO 2 RR using pure Cu 2 O is carried out, like Cu 2 O structure and electrolyte composition. Persistent Cu + is found to be key for selective CO 2 RR, especially favoring the formation of C2 product (CH 3 COOH). The Cu 2 O film thickness, local pH, and the electrolyte cations are revealed to influence the amount of surface Cu + . The number of H + and dissolved CO 2 affected by electrolytes also account for the disparity of CO 2 RR results. Therefore, by considering both the CO 2 RR and the dynamic change of Cu 2 O, this work has provided a compositional descriptor to link the structure of Cu 2 O and the CO 2 RR property, which can be useful for future development of Cu 2 O-based catalysts.