Synthesis And Photocatalytic Activities Of Mesoporous Bi₂WO₆ Nanoplates Modified By Cocatalysts

Bi₂WO₆ photocatalyst has promising chemical stability and narrow band gap and has widely been used in the field of photocatalytic oxidation or hydrogen production.However,pure Bi₂WO₆ suffers from the rapid recombination of electron-hole pairs,low quantum efficiency,and low photocatalytic activity.Herein,we hybridize Bi₂WO₆nanoplates with two kinds of cocatalysts,N-CQDs and MXene,to boost the charge separation and improve the photocatalytic activities.The main research includes:N-CQDs/Bi₂WO₆ composite photocatalysts were prepared by a one-step hydrothermal method,and the photocatalytic degradation of rhodamine B?RhB?was evaluated under visible light irradiation.We characterized its phase,morphology,photocatalytic performance and photocatalytic mechanism.The results show that N-CQDs/Bi₂WO₆ nanoplates with porous structures have been synthesized successfully,which exhibit a promising catalytic activity for the photodegradation of RhB.It is found the photocatalytic enhancement of N-CQDs/Bi₂WO₆ is attributed to the excellent electron trapping ability of N-CQDs and broadening absorbance of the visible light.The resulting N-CQDs/Bi₂WO₆ photocatalyst shows good application prospects in degrading organic pollution.MXene/Bi₂WO₆ photocatalyst was synthesized by electrostatically attracting negatively-charged MXene onto the positively-charged B_i2WO₆ nanoplatets.The photodegradation of VOCs under visible light were performed to evaluate the photocatalytic activity of the resulting catalyst.The introduction of MXene significantly enhances the photocatalytic performance of MXene/Bi₂WO₆.In addition,the loading amount of MXene has a great influence on the catalytic activity of MXene/Bi₂WO₆.MXene/Bi₂WO₆ exhibits the optimal photocatalytic performance at the MXene loading of 4 wt.%.The CO₂ production rates by the oxidation of C₃H₆O and CH₂O were 0.0728 mmol g^-11 h^-1 and 0.0853 mmol g^-11 h^-1,respectively,which were 2and 6.6 times higher than that of pure Bi₂WO₆.The results of mechanism study show that the increase in photocatalytic performance of MXene/Bi₂WO₆ is due to the coupling of MXene and Bi2WO6 rather than the enhancement of light absorption.Because MXene itself has a superior electronic conductivity similar to graphene,the photogenerated electrons can be rapidly injected into MXene through the coupling interfaces,which can effectively separate the photogenerated carriers.At the same time,the interfacial interaction between MXene and Bi₂WO₆ results in a positive shift of the valence band of Bi₂WO₆.The shift enhances the oxidizing ability of the photogenerated h⁺in the VB of Bi₂WO₆.The efficient separation of photogenerated carriers,the tightly coupling interface and stronger oxidation potential account for the improvement of photocatalytic performance.This work provides a new idea for improving the catalytic performance of semiconductor photocatalysts.