Insights into the multiple effects of oxygen vacancies on CuWO4 for photoelectrochemical water oxidation

Abstract

The multiple effects of oxygen vacancies on a CuWO₄ photoanode for photoelectrochemical water oxidation are investigated. A shorter electron transfer time across the photoanode is obtained for CuWO₄ with oxygen vacancies as compared to the pristine CuWO₄. This provides direct evidence of the enhanced electrical conductivity for CuWO₄ by oxygen vacancies. The water oxidation kinetics of CuWO₄ is also found to be boosted by oxygen vacancies. This experimental result is further investigated using density functional theory calculations, which reveal that the activation barriers for H₂O dehydrogenation on the surface of CuWO₄ with oxygen vacancies are much lower than those of CuWO₄. Interestingly, despite these advantages, oxygen vacancies are also found to be charge recombination centers on the photoanode's surface.