Blocking the reverse reactions of overall water splitting on a Rh/GaN-ZnO photocatalyst modified with Al2O3

Sunlight-driven photocatalytic overall water splitting (OWS) presents a promising route towards solar-to-chemical energy conversion. However, OWS has been realized with only a few photocatalysts. Among the major reasons for this paucity are the reverse reactions that occur between OWS products, including hydrogen, oxygen and reactive intermediate species, on the photocatalyst surface. In this study we found that decorating the Rh co-catalyst of the benchmark photocatalyst GaN-ZnO with Al2O3 species by atomic layer deposition can suppress these reverse reactions to a great extent and consequently enhance the photocatalytic OWS activity by more than an order of magnitude, with an apparent quantum efficiency increase from 0.3% to 7.1% at 420 nm. The partial coverage of Rh surface sites with inert oxides can effectively suppress the reverse reactions by blocking the reduction/oxidation cycle of Rh atoms during the photocatalytic OWS reaction.

Automated summary

Sunlight-driven photocatalytic overall water splitting (OWS) is a promising approach for solar-to-chemical energy conversion, but only a few photocatalysts have been successful. In this study, we found that decorating the Rh co-catalyst on GaN-ZnO photocatalyst with Al2O3 by atomic layer deposition can significantly suppress reverse reactions and enhance the photocatalytic OWS activity by more than an order of magnitude, with an increase in apparent quantum efficiency from 0.3% to 7.1% at 420 nm. The partial coverage of Rh surface sites with inert oxides effectively blocks the reduction/oxidation cycle of Rh atoms during the photocatalytic OWS reaction, leading to the suppression of reverse reactions.