AUTHOR=Gu Xiaosong , Luo Yujie , Li Qi , Wang Rui , Fu Shiqi , Lv Xiulong , He Qian , Zhang Ying , Yan Qiutong , Xu Xuan , Ji Fangying , Qiu Yan 

TITLE=First-Principle Insight Into the Effects of Oxygen Vacancies on the Electronic, Photocatalytic, and Optical Properties of Monoclinic BiVO4(001)

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.601983

DOI=10.3389/fchem.2020.601983

ISSN=2296-2646

ABSTRACT=<p>In this paper, first-principle calculations were performed to investigate the effects of oxygen (O) vacancies (Ovac) on the crystal structure, electronic distribution, adsorption energies of O<sub>2</sub> and H<sub>2</sub>O and the density of states (DOS) of monoclinic bismuth vanadate (m-BiVO<sub>4</sub>). Ovac were stable when incorporated into m-BiVO<sub>4</sub>(001) and increased the adsorption energy of O<sub>2</sub>. Ovac changed the V3d orbitals of m-BiVO<sub>4</sub>(001) by adding a new band gap level, causing the redundant electrons of V atoms to become carriers and promoting the separation efficiency of electrons and holes. To verify the first-principle calculations, m-BiVO<sub>4</sub> with different Ovac levels was prepared via hydrothermal synthesis. X-ray diffraction (XRD) patterns confirmed the existence of the (001) crystal surface of m-BiVO<sub>4</sub>. In addition, X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy of m-BiVO<sub>4</sub> confirmed the presence of Ovac and demonstrated that, as the Ovac level increased, the number of superoxide radicals (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>O</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup><mml:mo>·</mml:mo></mml:math></inline-formula>) and hydroxyl radicals (·OH) produced increased. In addition, m-BiVO<sub>4</sub> with a higher Ovac level possessed superior photocatalytic properties to and degraded rhodamine B (RhB) dye nearly 2-fold faster than m-BiVO<sub>4</sub> with a lower Ovac level. Finally, the removal rate of RhB increased from 23 to 44%. All experimental results were in good agreement with the first-principle calculated results.</p>