In situ growth of WO_{3- x} nanowires on g-C₃N₄ nanosheets: 1D/2D heterostructures with enhanced photocatalytic activity

We have constructed a new type of 1D/2D heterostructure by growing WO_3-x nanowires on the surface of g-C₃N₄ nanosheets through a simple solvothermal method. The created WO_3-x/g-C₃N₄ heterojunction allows for effective electron transfer from excited g-C₃N₄ nanosheets to WO_3-x nanowires, which leads to enhanced photocatalytic activities for methyl orange (MO) degradation. Further studies by using different active species as capture agents reveal that superoxide radicals are mainly responsible for MO degradation. The enhanced photocatalytic activity over the WO_3-x/g-C₃N₄ heterojunction is attributed to the abundant oxygen vacancies on the WO_3-x nanowire surface, which results in a considerable amount of free electrons on WO_3-x nanowires with promoted conductivity. As such, the injected photo-electrons from g-C₃N₄ can freely transport along the WO_3-x nanowires to promote charge separation on g-C₃N₄. Further, the large nanowire surface with strong capability for O₂ adsorption would provide the injected electrons with a high chance to reduce the surface adsorbed oxygen molecules and generate superoxide radicals for MO degradation.