Alkali Metal Chloride Flux Growth of Ilmenite-Type ZnTiO₃ and Subsequent Nitrogen Doping for Visible-Light-Driven Water Oxidation Catalysis

The polyhedral-shaped ilmenite-type ZnTiO3 crystals with well-developed facets were grown from alkali metal chloride fluxes (ACl, A = Li, Na, K, Rb, and Cs). NaCl and CsCl were observed to be the most suitable fluxes for growing ilmenite-type ZnTiO3 crystals without impurity phases. Doping nitrogen into the crystals was achieved via heating under the continuous flow of ammonia gas (NH3). The resulting crystals exhibited enhanced photon harvesting capacity while still maintaining their original crystal phase (i.e., ZnTiO3). The introduction of nitrogen into the lattice was confirmed through analytical techniques used for investigating the surface chemical states and bulk chemical compositions. The N-doped ZnTiO3 served as a competent photocatalyst for water oxidations in AgNO3 aqueous solutions under visible light irradiation.