Mechanism of incorporation of zirconium into BiVO₄Visible-Light Photocatalyst

Monoclinic BiVO4 is a promising material for realizing low-cost visible-light water splitting. Here, we report the incorporation mechanism of Zr into solution-processed BiVO4. Characterization of the crystal structure confirmed the incorporation of Zr into the BiVO4 lattice and the formation of single-phase monoclinic crystals at lower Zr concentrations. Characterization of the electronic stucture suggested that Zr acts as a shallow donor indicated that Zr acts as a shallow donor. The Zr-doped sample showed higher electrical conductivity than the undoped one and significantly enhanced photocatalytic activity at an optimum doping level of 0.1 mol %. Characterization of the local structure around Zr by X-ray absorption spectroscopy revealed a Zr4+ center in an 8-coordinated dodecahedral environment, indicating incorporation of Zr as a substitute on Bi site in the BiVO4 host. However, we have found that ZrBi substitution generates local lattice distortion, which, in turn, may cause the formation of more oxygen vacancies (VO) along with ZrBi-VO defect complexes, thus leading to lower Zr donor efficiency and increased nonradiative recombination. High Zr doping provokes the formation of mixed-phase BiVO4 crystals, resulting in low photocatalytic activity. The incomplete self-compensation of Zr in BiVO4 below the solubility limit suggests a potential for substitutional n-type doping of BiVO4 by group IV elements, paving the way for developing efficient BiVO4 basedphotocatalytic materials.