Fundamental bulk/surface structure-photoactivity relationships of supported (Rh_2-yCr_yO₃)/GaN photocatalysts

The supported (Rh_2-yCr_yO₃)/GaN photocatalyst was examined as a model nitride photocatalyst system to assist in the development of fundamental structure-photoactivity relationships for UV activated water splitting. Surface characterization of the outermost surface layers by high-sensitivity low energy ion scattering (HS-LEIS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) revealed that the GaN support consists of a GaO_x outermost surface layer on a thin film of GaO_xN_y. HR-XPS demonstrates that the supported (Rh _2-yCr_yO₃) mixed oxide nanoparticles (NPs) consist of Cr³⁺ and Rh³⁺ cations that are surface enriched for (Rh_2-yCr_yO₃)/GaN. Raman and UV-vis spectroscopy show that the bulk molecular and electronic structures, respectively, of the GaN support are not perturbed by the deposition of the (Rh_2-yCr_yO₃) NPs. The function of the GaN bulk lattice is to generate photoexcited electrons/holes, with the electrons harnessed by the surface Rh³⁺ sites for evolution of H₂ and the holes trapped at the Ga oxide/oxynitride surface sites for splitting of water and evolving O₂.