Structure, Electronic Properties, and Defect Chemistry of Delafossite CuRhO2 Bulk and Surfaces

CuRhO2 in the delafossite structure is a promising, highly stable photocathode material for solar water splitting, yet the fundamental bulk and surface properties of CuRhO2 that are relevant to such an application have rarely been studied. In this work, we present a comprehensive computational study of the bulk and majority (001) surface of CuRhO2 using density functional theory at the meta-GGA and hybrid functional levels. For bulk CuRhO2, our results show a significant degree of hybridization between Rh, Cu, and oxygen states near the valence band maximum suggesting a high hole mobility in this material in comparison to other Cu-delafossite oxides. The typical Cu vacancy and Cu antisite defects are predicted to behave as shallow acceptors in bulk CuRhO2; they do not trap charge carriers and should not act as electron-hole recombination centers under photoexcitation. The computed surface stability diagram under vacuum conditions shows that CuRhO2 (001) typically exposes the Rh/O termination with empty surface states in the lower half of the band gap. Cu antisite defects can however form on this surface, leading to deep hole states that can trap electrons and favor the recombination of photoexcited carriers. Overall, the present results provide fundamental insight into the properties of intrinsic defects in the bulk and at the surface of CuRhO2. This knowledge is an essential basis for an investigation of the photo-electrochemical performance of this material.