Direct Z-scheme hierarchical WO3/BiOBr with enhanced photocatalytic degradation performance under visible light

A visible light-driven 3D hierarchical photocatalyst WO3/BiOBr (WB) was prepared by solvothermal method, through which 2D BiOBr ultra-thin nanosheets grew on 1D WO3 nanotube bundles. The as-prepared WB-0.5 (i.e. W:Bi with a mole ratio of 0.5:1) had the highest photocatalytic degradation efficiency of 94.7% for ciprofloxacin hydrochloride under visible light irradiation (λ > 400 nm) within 120 min; such efficiency was about 5.2 and 1.6 times higher than that of individual WO3 and BiOBr, respectively. Its removal rate of total organic carbon was 41.2%. Moreover, WB-0.5 showed high reusability and photostability, and its photocatalytic activity did not show any obvious decrease even after five cycles. The characterisation of WB-0.5’s crystal structure, morphology, and surface elemental state confirmed its 3D hierarchical structure and formation of heterojunction. Its direct Z-scheme system was tested by analysing the active species, photocurrent characteristics, Mott–Schottky plots, UV-vis diffuse reflection spectroscopy and in situ irradiation XPS. The 3D hierarchical structure may provide increased active sites and enhanced light absorption efficiency. The direct Z-scheme configuration is particularly beneficial for improving photocatalytic activity. Therefore, this work may provide a feasible strategy for designing a Z-scheme 3D hierarchical photocatalyst.