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 application have rarely been studied. Here, 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. First, we examine the structure, thermodynamic and electronic properties of pristine and defective bulk CuRhO₂, addressing the potential role of bulk defects in the behavior of charge carriers. Our calculations show that Cu vacancies and Cu antisite defects introduce shallow acceptor levels in line with the results for bulk CuFeO₂. The computed surface stability diagram for CuRhO₂(001) under vacuum conditions shows that Cu antisite defects can be favorable also at the surface. Analysis of the electronic structure of pristine and defective surfaces allows us to identify the surface (trapping) states and their dependence on the local structure. Finally, we discuss the influence of bulk and surface defects on photoelectrochemical performance.