Preparation of La doped BiVO4 under weak acid environment to enhance (040) crystal plane exposure and photocatalytic activity: characterization and degradation mechanism

Abstract

In this paper, a 0.0%-5-BVO sample with (040) crystal plane exposure was successfully prepared by a hydrothermal method in a pure aqueous-phase environment free of organic solvents by modulating the pH of the precursor solution, and its I040/I-121 reached 1.70, which is 6.8 times that of the standard PDF#14–0688. Subsequently, a 4.0%-5-BVO sample was prepared by using La(NO3)3–6H2O as the La source to further promote the (040) crystal plane exposure via La. The I040/I-121 of the 4.0%-5-BVO sample reached 3.05, which was 12.2 times that of the standard PDF#14–0688, and exhibited stronger photocatalytic activity compared with that of the 0.0%-5-BVO. In addition, a correlation between precursor solution pH and the crystalline phase of BiVO4 was observed, with increasing pH and decreasing sample I-121/I200 from 4.32 for 4.0%-3-BVO to 0.34 for 4.0%-9-BVO, with decreasing monoclinic and increasing tetragonal phase content. La also had an effect on the crystalline phase, causing I-121/I200 to decrease from pre-doped 8.85 before doping to 2.70 after doping, contributing to the change of BiVO4 toward the tetragonal phase.