Roles of Rh/Cr₂O₃ (Core/Shell) Nanoparticles Photodeposited on Visible-Light-Responsive (Ga_1-<i>_x</i>Zn<i>_x</i>)(N_1-<i>_x</i>O<i>_x</i>) Solid Solutions in Photocatalytic Overall Water Splitting

Photodeposited Rh/Cr2O3 (core/shell) nanoparticles on a (Ga1-xZnx)(N1-xOx) photocatalyst are studied as a cocatalyst for overall water splitting. Irradiation of Rh-loaded (Ga1-xZnx)(N1-xOx) with visible light (λ > 400 nm) in aqueous K2CrO4 solution results in the formation of core/shell-structured nanoparticles consisting of a Rh core and Cr2O3 shell through the site-selective photoreduction of CrO42- anions to Cr2O3 on Rh nanoparticles. The shell thickness increases with concentration of K2CrO4 in the reactant solution to a maximum of ca. 2 nm, at which a uniform Cr2O3 coating is obtained. The Cr2O3 shell suppresses water formation from H2 and O2 on Rh nanoparticles, allowing stoichiometric decomposition of pure water to be achieved. The core/shell structure also provides enhanced H2 evolution compared to that of bare Rh nanoparticles.