A visible-light-sensitive water splitting photocatalyst composed of Rh3+ in a 4d6 electronic configuration, Rh3+-doped ZnGa2O4.

Using the Rh(3+) ion (Rh d(6)) in a regular octahedral coordination, which forms fully occupied t(2g)(6) and empty e(g)(0) as a result of ligand-field splitting, we demonstrated that Rh-doped ZnGa(2)O(4) had midgap states created by t(2g)(6) and e(g)(0) that had suitable potentials to produce either hydrogen or oxygen in the presence of sacrificial agents under visible-light irradiation.