Roles of Bi, M and VO4 tetrahedron in photocatalytic properties of novel Bi0.5M0.5VO4 (M=La, Eu, Sm and Y) solid solutions for overall water splitting

Novel Bi0.5M0.5VO4 (BMV; M=La, Eu, Sm and Y) solid solutions were prepared and studied in this paper. All the samples were proved to produce H2 and O2 simultaneously from pure water under the irradiation of UV light. M–O bond lengths were proved to increase with M cations by refining cell parameters and atomic positions. Besides, band gaps, energy gaps and photocatalytic activities of BMV also changed with M cations. Both of M–O and V–O bond lengths were suggested to account for this phenomenon. Inactive A0.5Y0.5VO4 (A=La, Ce) for water splitting proved incorporation of Bi rather than distortion of VO4 tetrahedron was a critical factor for improving efficiency of overall water splitting by facilitating the generation of electron and hole with lighter effective masses. Replacement of Bi by M cations not only gave indirect effect on band structure but also raised position of conduction band minimum to meet requirement of H2 production.