In-situ formation of WO3/WS2 heterojunction for an efficient and stable NO abatement under visible light

Abstract

Tungsten trioxide (WO₃) with a suitable bandgap for environmental photocatalysis exhibits susceptibility to photocorrosion/photochromism stemming from the instability of W⁶⁺, which undergoes reduction to lower valence states. To achieve a stable photocatalytic NO abatement, a heterostructure comprising nano-sized tungsten disulfide (WS₂) dots on WO₃ planar sheets was synthesized via a single-step calcination of WS₂ at different temperatures. Charge transfer at the WS₂/WO₃ interface suppresses the photocorrosion of WO₃ during the photocatalytic NO abatement. The optimized WS₂/WO₃ heterostructure demonstrated an NO removal efficiency that is 2.5 times higher than that of pristine WO₃ and exhibited robust stability during cyclic tests. WS₂ alone displayed negligible photocatalytic activity toward NO oxidation, but WS₂ facilitated the electron diversion on WO₃ via a S-scheme mechanism, minimizing the reduction of W⁶⁺. The reactive oxygen species (ROS) generated on WS₂ has to initiate the oxidation of NO that is activated at the WS₂/WO₃ interface. This study elucidates a promising methodology for constructing heterostructure with an intimate interfacial contact and an optimized charge transfer for the efficient oxidation of NO under the ambient atmosphere.