Insights into the multiple effects of oxygen vacancies on CuWO₄for photoelectrochemical water oxidation

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.