Preparation Of Composite WO₃ Thin Film Electrode And Its Photocatalytic Properties

Coking wastewater contains a variety of complex organic matters,which has a significant harm to the ecological environment and human health.In many treatment methods,on the basis of photocatalytic technology,the photoelectrocatalytic?PEC?technology increases the applied voltage,which can further enhance the photocatalytic activity of the catalyst.It is considered to be an ideal technology to realize the complete decomposition of organic pollutants in wastewater.WO₃ has attracted widespread attention in terms of organic degradation due to its good physical and chemical stability,non-toxicity and sensitive light response.However,WO₃ has fewer surface active sites and cannot absorb the full range of visible light,making the photocatalytic activity less than expected.This study starts from two aspects:On the one hand,it is to design the electrode morphology that is beneficial to contact with organic wastewater,refine the grains,increase the specific surface area of the material,and increase the number of active sites.On the other hand,a suitable material is selected for recombination with WO₃ to build a heterojunction,and the built-in electric field formed at the material recombination interface is used to promote the separation of photogenerated electrons and holes.The specific research content is as follows:?1?Using the hydrothermal growth method,a WO₃ thin-film electrode with a flat surface and a good bonding force was prepared on the FTO substrate.Through phase characterization,it is proved that WO₃ has good crystallinity,all of which are monoclinic crystals with a grain size of about 17.0 nm.A large number of nano-sheet WO₃ grows approximately vertically on the surface of FTO and intersect to form a 3D porous micro-morphology.Photoelectrochemical testing showed that the photocatalytic degradation efficiency of pure WO₃ thin-film electrode for methylene blue solution?MB?was only23.8%.?2?In order to improve the catalytic activity of the WO₃ thin film electrode,the BiOI/WO₃ thin film electrode was prepared by electrodepositing BiOI on its surface.The BiOI/WO_3-120s thin film electrode has the best catalytic activity and the degradation efficiency is 86.7%,which is 3.6 times that of the pure WO₃ thin film electrode.It is shown that the composite of BiOI is beneficial to significantly improve the photocatalytic activity of WO₃ thin film electrodes.A trapping experiment show that the active materials are h⁺and·OH,which means that BiOI/WO₃ has only oxidation and no reduction and is an oxidative photocatalyst.?3?In order to further improve the catalytic activity of the electrode,the CdS/BiOI/WO₃ thin-film electrode was prepared by using the SILAR method.The sensitized electrode can not only absorb all the visible light,but also part of the near-infrared light.The light utilization ratio is ideal.This is due to the large reduction of the band gap?Eg?of the sensitized electrode.The sensitized electrode is a direct Z-scheme ternary heterosemiconductor.The unique photo-generated carrier transport path can reduce the transmission resistance and improve the electron-hole separation efficiency.A trapping experiment showed that the active materials were·O^2-and h⁺,indicating that the CdS/BiOI/WO₃ thin-film electrode has both oxidizing and reducing properties.The degradation efficiency of CdS/BiOI/WO₃ thin film electrodes is as high as 98.3%.Therefore,CdS QD sensitization is beneficial to further improve the photocatalytic activity of BiOI/WO₃ thin film electrodes.