Theoretical Insights into Photoelectrochemical Water Reduction on Delafossite CuRhO₂

Delafossite CuRhO2 is a p-type semiconductor capable of reducing water efficiently and durably under visible light illumination. To obtain fundamental insight into these properties, we investigated the CuRhO2(001)/water interface in electrochemical environment using density-functional theory coupled with an implicit water solvent model for the electrolyte. We determined how the solvent affects the surface structure under applied voltage and controlled pH and computed the corresponding band offsets at the aqueous interface. The band alignment of the partially reduced CuRhO2/water interface shows a suitable conduction band edge for the hydrogen evolution reaction (HER), in agreement with experiment. Rh-based surface states close to the conduction band are predicted not to act as recombination centers but possibly favor the HER. Moreover, proton discharge leads to the formation of weakly adsorbed species, suggesting CuRhO2 as an effective photocatalyst for this reaction.