Preparation Of WO₃ Photocatalytic Films By Magnetron Sputtering Method And Their Heterojunction Structure Modification

In recent years,semiconductor material photocatalysis technology for degrading water contaminants has received widespread attention.As an ideal water treatment method,WO₃photocatalysis technology can utilize solar energy source with a stable photocatalytic reaction process,thorough degradation of contaminants,and non-toxic material.WO₃ with a band gap energy?Eg?of 2.7 eV can be used as a visible light responsive photocatalyst.Therefore,it is widely considered as a new photocatalytic material for water purification.In this study,WO₃ films were prepared using the mid-frequency reactive magnetron sputtering method at varying reaction gas ratios and substrate biases.As well,the impregnating-precipitation-photoreduction method was used to modify the prepared films.The optical and structural properties of the prepared films were characterized by X-ray diffraction?XRD?,field emission scanning electron microscope?FE-SEM?,atomic force microscopy?AFM?,Raman spectra and absorbance spectra.The photocatalytic activity of the thin films was evaluated by measuring the photodecomposition of methylene blue?MB?under a fluorescent lamp.The experiments on the annealed films reveal a hexagonal structure and have some absorptivity in the visible region.The field emission scanning electron microscopy pattern shows that the films exhibit a uniform,smooth surface.The films exhibit the best activity at an oxygen flow rate of 30 sccm and a substrate bias of-50 V.In the impregnating-precipitation-photoreduction method,Ag/AgCl particles are loaded onto the surface of WO₃ films.WO₃ films decorated with Ag/AgCl can greatly enhance photocatalytic efficiency under visible light.Due to the interface of heterojunction structure of Ag/AgCl and WO₃,the transport and separation efficiency of photogenerated charges are enhanced.Ag/AgCl/WO₃-3 film has 1.81 times optimal photocatalytic activity higher than that of WO₃ films.The experiments on the modified films showed the films have higher surface area and higher absorption efficiency in the visible region.The main active radicals in the photodegradation process are superoxide radicals?·O₂^-?and holes?h⁺?.A possible photocatalytic mechanism is proposed based on the test results.In addition,the tests show that the photocatalytic efficiency of the films is not significantly reduced after reusing 3 times.Herein,the WO₃ film catalysts were comparatively stable and easy to recycle.