Photocatalytic Degradation of Volatile Organic Compounds over WO2/SnS2 Nanofibers

Solar-powered volatile organic compound oxidation attracts interest, but its efficiency suffers from poor utilization of photogenerated electrons. Oxygen can capture the electrons and convert them into superoxide radicals upon being activated. As a unique oxygen-deficiency oxide, WO2 chemisorbs and activates oxygen and functions as a potential cocatalyst for improving the utilization of charge carriers. Here, we report a WO2/SnS2 composite photocatalyst with SnS2 nanosheets vertically growing out of WO2 nanofibers. In situ X-ray photoelectron spectroscopy and density functional theory calculations suggest the electron transfer from WO2 to SnS2, creating an internal electric field (IEF) at the interfaces with a direction pointing from WO2 to SnS2. The IEF promotes spatial charge separation by driving photogenerated electrons in SnS2 to move to WO2, while photogenerated holes remain immobile. WO2 shows a strong affinity for oxygen-containing species and chemisorbs O2 and H2O molecules in a dissociative way, significantly reducing the kinetic barriers for the production of reactive oxygen species (•OH and •O2–). Under visible light irradiation, the WS30 nanofibers exhibit enhanced photocatalytic degradation of HCHO and CH3COCH3, 4.8 and 7.2 times greater than that of pristine SnS2, respectively. The enhanced performance is attributed to the one-dimensional fibrous nanostructures, robust chemisorption of reactants, and IEF-driven charge separation. This work may inspire efforts to develop higher oxygen-affinity photocatalysts for photodegradation.