Substitution Effects of the Trivalent Cations M³⁺ on the Photophysical and Photocatalytic Properties of In₁₂NiM₂Ti₁₀O₄₂ (M = Al, Cr, Ga)

Abstract

A new series of visible-light-driven photocatalysts In₁₂NiM₂Ti₁₀O₄₂ (M = Al, Cr, Ga) with a pyrochlore-related layered structure were synthesized by the conventional solid-state reaction method. The substitution effects of trivalent cations M³⁺ on the electronic structure, photophysical and photocatalytic properties were investigated. It was found that although the three materials were all crystallized in a monoclinic symmetry with the same space group P2₁/a, their photocatalytic activities of H₂ evolution were quite different. In comparison with In₁₂NiAl₂Ti₁₀O₄₂ and In₁₂NiGa₂Ti₁₀O₄₂, In₁₂NiCr₂Ti₁₀O₄₂ showed the narrowest band gap and highest activity, which could be ascribed to the formation of broadly dispersed continuous conduction and valence bands due to the involvement of partially filled Cr 3d orbitals in addition to Ni 3d orbitals. The present study suggests a promising method for developing visible-light-driven photocatalysts with tailored properties via transition-metal(s)-mediated band structure engineering.