Fabrication of WO3 photocatalyst by plasma assisted ball milling under different discharge atmospheres

A convenient method for producing single oxide WO 3- x at room temperature through plasma milling was reported, resulting in a highly efficient visible-light photocatalyst . By altering the discharge atmosphere during plasma milling from ammonia and nitrogen to argon, the color of the milled monoclinic WO 3 powders deepens from blue to dark blue, indicating an increased concentration of oxygen vacancies . The morphological and structural properties of the monoclinic WO 3 powders, prepared using different ball milling techniques, are characterized using XRD , SEM, TEM , Raman, XPS , EPR, and UV–vis. These results reveal that plasma milling leads to a higher surface area, increased presence of oxygen vacancies, and more defects compared with conventional milling, resulting in a greater number of more reactive sites and a larger contact area between monoclinic WO 3 nanoparticles and RhB solution. Consequently, monoclinic WO 3 samples fabricated through Ar-P-milling exhibit the highest photocatalytic activity . This is attributed to the reduction of the WO 3− x band gap to 2.28 eV by Ar-P-milling with high oxygen vacancies. This lower bandgap markedly improves the light utilization rate, thereby enhancing the overall photocatalytic efficiency. The Ar-P-milled WO 3 shows the highest degradation rate constant of 0.037 min −1 , which is 4 times higher than that of pure monoclinic WO 3 .