Robust Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 for efficient degradation of phenolic pollutants

Abstract

Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 are facilely fabricated via a thermal-induced self-polymerization of melamine in the presence of WO3 nanowires, nanosheets and microflowers, and they are successfully applied in simulated sunlight photocatalytic degradation of two refractory phenolic pollutants, p-nitrophenol and methylparaben. The g-C3N4/WO3 heterojunctions exhibit enhanced photocatalytic removal efficiency towards the target pollutants in comparison of pristine g-C3N4 and WO3; moreover, both the ratio and morphology of WO3 influence the photocatalytic activity of g-C3N4/WO3 dramatically. At the same ratio of WO3 in heterojunctions, g-C3N4/WO3 nanowires exhibit the highest pollutants removal efficiency among three heterojunction photocatalysts. By combination of testing results including photoelectronchemistry, photoluminescence and active species trapping it is confirmed that the unique Z-scheme band alignment of g-C3N4/WO3 heterojunctions plays the dominated role to the enhanced photocatalytic activity, which not only boosts the spatial separation of charge carriers but also endows the g-C3N4/WO3 with supreme redox capacity; additionally, intimate interfacial contact between WO3 and g-C3N4 in the heterojunctions can further promote this Z-scheme-dictated charge carrier transfer and separation. Under the attack of active species like hVB+, O2− and OH radicals, the target pollutants can be oxidized deeply to harmless inorganic compounds.