Nonstoichiometric tungsten oxide residing in a 3D nitrogen doped carbon matrix, a composite photocatalyst for oxygen vacancy induced VOC degradation and H2 production

Abstract

With a coordination complex modified polyoxometalate compound and filter paper as precursors, an oxygen vacancy rich composite photocatalyst (WO_3−x/NC) composed of nonstoichiometric tungsten oxide (WO_3−x, 1 > x > 0) and a 3D nitrogen doped carbon matrix was synthesized successfully. In WO_3−x/NC, WO_3−x nanoparticles with a size of about 3 to 6 nm are dispersed homogenously in a 3D nitrogen doped carbon matrix. The existence of oxygen vacancies has been confirmed by electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). WO_3−x/NC exhibits remarkable photocatalytic activity for the degradation of volatile organic compounds (VOCs). Under visible light irradiation it can completely degrade formaldehyde and benzene in 90 min. The durability of WO_3−x/NC is also excellent. After 8 successive reaction cycles the removal rate stays as high as 92%. More importantly, WO_3−x/NC also exhibits outstanding visible and near-infrared light driven photocatalytic H₂ evolution activity. The prominent VOC removal and H₂ production properties can be attributed to the oxygen vacancies from WO_3−x and the good conductivity of the nitrogen doped carbon matrix. We hope WO_3−x/NC can be applied as an effective material in air purification and H₂ energy development.