Exploration of a novel Type II 1D-ZnO nanorods/BiVO₄ heterojunction photocatalyst for water depollution

In this study, we reported on the successful fabrication of a novel heterojunction photocatalyst (in particulate system) with a Type II band alignment between 1D-ZnO nanorods and BiVO₄ nanocrystals. Pristine 1D-ZnO nanorods and BiVO₄ nanocrystals were first fabricated through hydrothermal reaction followed by heterojunction formation via the wet chemical reaction. The 1D-ZnO/xBiVO₄ heterojunction photocatalyst (x = weight ratio of BiVO₄ in g) that found optimum when x = 0.08 g was used for the degradation of salicylic acid (SA) and Reactive Black 5 (RB5) resulting in high pseudo-first-order reaction rate constants of 0.0049 min⁻¹ and 0.0132 min⁻¹, respectively. Electrochemical studies proved that the 1D-ZnO/0.08BiVO₄ heterojunction photocatalyst demonstrated a fast charge mobility and the most efficient photogenerated charge carriers separation among other heterojunction samples as analysed from PL spectra. Besides, UV–vis spectroscopic measurement and optical characterisation showed that the improved photoactivity in 1D-ZnO/BiVO₄ is attributed to the formation of a Type II heterojunction staggered arrangement that enables a broader visible-light harvesting ability. Finally, a postulation photocatalytic mechanism was proposed based on the theoretical band alignment diagram between the 1D-ZnO nanorods and BiVO₄ nanocrystals as well as portraying the fundamental charge carriers transfer within the 1D-ZnO/BiVO₄ heterojunction photocatalyst.