Phase Transition And Photocatalytic Improvement Of Nd-,Pr-,and Lu-doped BiVO₄

Bismuth vanadate?BiVO₄?is a narrow band gap semiconductor with strong performance of pollutant degradation.BiVO₄ displays phase transition via rare earth ions doping to form diphase heterojunction.This structure accelerates electron-hole separation to improve catalytic efficiency.However,improvement mechanism of neodymium?Nd?doping has not been studied from energy band theory.In addition,BiVO₄ phase transformation has not been reported via praseodymium?Pr?,and lutetium?Lu?doping.In this paper,Nd,Pr,and Lu-doped BiVO₄powders are synthesized by hydrothermal method.The tuning mechanism of photocatalytic activity BiVO₄ and phase transition process are explored in detail.Monocline BiVO₄ displays Nd concentration dependent on lattice transition through X-ray diffraction?XRD?and Raman peak analysis.Pure tetragonal BiVO₄ is obtained in 9%at Nd-doped sample.Phase transition brings about morphology change from irregular particles through cuboid bars to spherical-like or groove nut-like surface.Due to regular shapes,rhodamine B degradation efficiency of all doping samples in full spectral conditionis higher than that of pure monocline phase.n-n type staggered energy band heterojunction is formed in the mixed phase by high resolution transmission electron microscopy and Mott-Schottky survey.Such energy band configuration promotes separation of photogenic carriers and inhibits their recombination.4%at Nd-doped samples has 99.4%degradation efficiency after 90 min.In addition,BET surface area,particle size,impedance and photocurrent of the sample plays a weak role in degradation rate.Pr and Lu-doped BiVO₄ also show crystalline phase transformation with 90%at doping concentration to obtain single phase tetragonal sample.Novel nanorods shapes appear in Pr and Lu-doped sample.Pr and Lu replace Bi sites with positive trivalent using X-ray photoelectron spectroscopy and energy dispersion spectra analysis.From elemental mapping image,Lu distributes uniformly in the sample.Pr and Lu doping induces blue shift of absorption edge and strong visible light absorption of Pr³⁺by diffuse reflectance spectrum test.5%at Pr and 15%at Lu doped samples have the optimum catalytic efficiency.After 90 minutes of illumination,the catalytic efficiency reached 89%and 100%respectively.Except for the influence of morphology and heterojunction,the range expansion of light response increases electron hole numbersin redoxreaction.It further shortens the degradation time to improve catalysis property.In summary,BiVO₄ phase transition has potential application prospects for improving photocatalytic performance by lanthanide doping strategy.