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Experimental and Computational Investigation of Lanthanide Ion Doping on BiVO4 Photoanodes for Solar Water Splitting C

Govindaraju, Gokul V., Morbec, Juliana M., Galli, Giulia A., Choi, Kyoung-Shin
Journal of physical chemistry 2018 v.122 no.34 pp. 19416-19424
bismuth, density functional theory, guidelines, oxygen, physical chemistry
N-type bismuth vanadate (BiVO₄) has emerged as one of the most promising photoanodes for use in water-splitting photoelectrochemical cells in recent years. However, its photoelectrochemical properties may be further enhanced by optimizing its band gap and its charge-transport properties. Doping at the V⁵⁺ and O²– sites of BiVO₄ has proven to be an effective strategy to alter the oxide electronic band structure and/or charge-transport properties, but the effect of doping at the Bi³⁺ site is not nearly as well understood. In this study, we performed a combined experimental and theoretical study of BiVO₄ doped with lanthanide (Ln) elements (La, Ce, Sm, and Yb) at the Bi³⁺ site, and we elucidated the effect of doping on the electronic band structure and charge-transport properties of BiVO₄. Furthermore, we performed density functional theory calculations to investigate the combined effect of the Ln doping and oxygen vacancies, which are intrinsic defects in BiVO₄. Our results showed that for some cases, the simultaneous consideration of Ln doping and O vacancy leads to changes that cannot be obtained by the sum of the changes caused by Ln doping alone and O vacancy alone, which was critical for understanding the experimental results. The various ways that the Ln dopants modified the electronic band structure and charge-transport properties of BiVO₄ demonstrated in this study can provide useful guidelines for the tuning of the composition of oxide-based photoelectrodes.