The role of the CeO2/BiVO4 interface in optimized Fe–Ce oxide coatings for solar fuels photoanodes

Abstract

Solar fuel generators entail a high degree of materials integration, and efficient photoelectrocatalysis of the constituent reactions hinges upon the establishment of highly functional interfaces. The recent application of high throughput experimentation to interface discovery for solar fuels photoanodes has revealed several surprising and promising mixed-metal oxide coatings for BiVO₄. Using sputter deposition of composition and thickness gradients on a uniform BiVO₄ film, we systematically explore photoanodic performance as a function of the composition and loading of Fe–Ce oxide coatings. This combinatorial materials integration study not only enhances the performance of this new class of materials but also identifies CeO₂ as a critical ingredient that merits detailed study. A heteroepitaxial CeO₂(001)/BiVO₄(010) interface is identified in which Bi and V remain fully coordinated to O such that no surface states are formed. Ab initio calculations of the integrated materials and inspection of the electronic structure reveals mechanisms by which CeO₂ facilitates charge transport while mitigating deleterious recombination. The results support the observations that addition of Ce to BiVO₄ coatings greatly enhances photoelectrocatalytic activity, providing an important strategy for developing a scalable solar fuels technology.