Preparation Of BiVO₄-CdS Composite Photocatalyst And Its Degradation Performance For Tetracycline

Photocatalytic technology has received widespread attention as an ideal way to solve the problem of environmental pollution and energy shortages.However,the photocatalytic process still has problems such as high electron-hole recombination rate,low degradation rate,and insufficient light absorption capacity.Therefore,this paper takes bismuth vanadate?BiVO₄?and cadmium sulfide?CdS?as the main research objects.The problems in the photocatalytic process were solved by constructing various Z-type composite photocatalysts.And the composite photocatalysts were characterized by different characterization methods.In addition,the performance of photocatalyst was evaluated by the degradation of tetracycline.Finally,the mechanism of tetracycline degradation by composite photocatalyst was analyzed.The specific research content is as follows:?1?The development of a highly efficient and rapid method for the accurate preparation of photocatalysts with novel morphologies is a hot research topic.The different morphologies of BiVO₄ was prepared by using surfactants assisted microwave method,and demonstrated irregular?no surfactant?,octahedral?sodium dodecyl benzene sulfonate?,olive-like?polyvinylpyrrolidone?and hollow structures?ethylenediaminetetraacetic acid?,respectively.The BiVO₄-CdS were synthesized using the chemical-bath-deposition method with different morphologies of BiVO₄ as the substrates.The hollow structure of BiVO₄ displayed the highest photocatalytic performance.Moreover,the photodegradation rates of the hollow structure BiVO₄-CdS on tetracycline hydrochloride was about 1.8 higher than the corresponding BiVO₄,indicating that the Z-scheme heterojunction can improve the photogenerated electron pairs separation efficiency.Furthermore,the regulation mechanism of morphology and energy-band position,as produced using the surfactants,has also been thoroughly investigated in this work,which provides a novel insight into the efficient and rapid preparation of photocatalysts with special morphology and high performance.?2?Interfacial charge separation and heterojunction system are conductive to improving its photocatalytic performance.Herein,we designed a novel photocatalyst of Z-scheme BiVO₄?040?-Ag@CdS,in which Ag was photo-deposition on the?040?facets of BiVO₄ as the??linker”between BiVO₄ and CdS.Characterizations of XRD and SEM clearly revealed that the BiVO₄?040?-Ag@CdS was prepared through hierarchical fabrication.The photoelectrochemical performances demonstrated BiVO₄with high proportion?040?facet and CdS with nanorods structure could drastically improve the photocatalytic performance.Then,the 100%BiVO₄?040?-Ag@CdS presented an excellent photodegradation rate towards tetracycline hydrochloride.This contribution provides a novel insight for improving the separation efficiency of photoelectronhole pair and photodegradate towards refractory organic pollutants.?3?Oxygen vacancies can effectively capture the electrons in the bismuth-based photocatalyst,and can act as an electron medium in the Z-Scheme photocatalyst,thereby improving the separation efficiency of photogenerated electron-hole pairs.Therefore,BiVO₄ in leaf shape was prepared by hydrothermal method,and Bi/BiVO₄ rich in oxygen vacancies were obtained by one step reduction method of sodium borohydride.Finally,Bi/BiVO₄-CdS photocatalysts were prepared by chemical bath deposition method.Bi/BiVO₄-CdS photocatalyst has the highest degradation rate of tetracycline.Analysis of the photocatalytic mechanism shows that Bi metal plays a role in enhancing light absorption in the photocatalytic system,and oxygen vacancies function as an intermediate carrier in the photocatalytic system to improve the separation efficiency of electrons and holes.This work provides a new direction for the development of oxygen vacancies and the use of Bi metals.