Benefits on photocarrier transfer from the transition of 3D to a 2D morphology

Abstract

The severe photogenerated carrier recombination of BiVO₄ leads to a poor performance and limits extensive commercial applications. Here, BiVO₄ nanocrystalline powder and epitaxial BiVO₄ films were prepared via a hydrothermal method and laser pulse deposition, respectively. The BiVO₄ powder had a typical morphology of a truncated tetragonal bipyramid, whereas the epitaxial BiVO₄ film was composed of nano-islands uniformly distributed on a (001)-oriented yttrium-stabilized zirconia (YSZ) substrate. Compared to three-dimensional (3D) nanocrystalline powder, nanoislands are much more approximate to a two-dimensional (2D) morphology. According to the results of rhodamine B degradation experiments under 440 nm monochromatic light irradiation, the apparent quantum yield increased by 1.75-times with the morphology transformation from 3D to 2D. The epitaxial BiVO₄ films had a more negative conduction band position, and exposed a larger ratio of the (010) facets, which were beneficial to the utilization of photogenerated electrons. In addition, the higher oxygen vacancy content of the BiVO₄ films was also conductive to the separation of photogenerated carriers. The synergistic effects of the 2D morphology and oxygen vacancies promoted the photocatalytic activity of epitaxial BiVO₄ films.