Preparation Of Bi₂WO₆/PDI Heterojunction Photocatalyst And Its Photocatalytic Performance Under Visible Light

Nowadays,human society is facing two major problems of environmental pollution and energy shortage.How to develop and utilize high efficiency and environmentally friendly solar energy has become the focus of attention.Semiconductor photocatalysis is an important technology of effective utilization of solar energy,which is mainly applied to the treatment of environmental pollutants and the production of chemical energy.However,there are two key problems in the current semiconductor catalysts that restrict its catalytic activity: 1.Low visible light utilization;2.Photoelectron-hole rapid recombination.In view of the above two problems,the following two aspects are mainly studied:1.The separation of photoelectrons and holes is closely related to the photocatalytic efficiency,and the construction of heterojunction can effectively promote the separation of photogenerated electrons and holes.The Bi2WO6/PDI heterojunction photocatalyst were prepared by a simple water bath heating method,which effectively improved the visible light photocatalytic activity of organic degradation and oxygen production rate than that of single photocatalyst.We explained that the enhancement of photocatalytic activity is mainly due to the formation of n-n type heterojunction structure at the contact interface between self-assembled PDI and Bi2WO6,and the surface hybrid of self-assembled PDI and Bi2WO6 promotes the separation of photogenerated carriers,and the electron transfer from the PDI LUMO orbital to the conduction band of Bi2WO6,which produces visible light degradation activity based on superoxide radical(O2·-).This study provides a way to improve the photocatalytic performance by constructing inorganic/organic n-n type heterojunction.2.Ion doping is also a method to improve the photocatalytic performance.The K+ and Clco-doped Bi2WO6/PDI based catalysts were synthesized by a one-pot thermal method.The doping of K+ and Cl-in Bi2WO6 crystals is confirmed by energy dispersive spectrometer(EDS)analysis and X-ray photoelectron spectroscopy(XPS)analysis.The synergistic effect of Bi2WO6 and PDI forms heterojunction structure with K+ and Cl-co-doped to achieve high efficient visible light photocatalytic rate.The UV-Vis diffuse reflectance spectra showed that the K+ and Cl-co-doped Bi2WO6/PDI based catalysts had wider visible light absorption than the Bi2WO6/PDI catalysts;The photocurrent and AC impedance spectra reflected K+,Clco-doped Bi2WO6 /PDI has more efficient photoelectron and hole separation efficiency than Bi2WO6/PDI.Both of them promote the performance of the catalyst after ion doping.DFT calculations show that K changes the coordination of O-Bi to facilitate carrier separation,and Cl insertion into the Bi-O-Bi sandwich reduces the bandgap of the material then extends visible light absorption.This research will provide new strategies for the preparation of efficient photocatalysts to meet the needs of environmental organic pollutants treatment.