Design,Synthesis,and Performance Manipulation Of Photocatalytic Degradation Of Organic Pollutants For ZnO-Based Semiconductor Nanostructures

Recently,for environmental pollution and increasing energy shortage,semiconductor-based photocatalysis has been considered as an approach to solve these problems.ZnO-based photocatalysts have been widely studied for their unique physicochemical properties and considered as one of the most important photocatalysts.However,it still suffers from fast carrier complexation and insufficient redox ability.For this,CdS@ZnO photocatalysts with different morphologies were designed and synthesized by hydrothermal/solventothermal method to improve those problems of ZnO-based photocatalysts.Furthermore,in order to improve the carrier complexation of ZnO,by doping Gd³⁺,and based on this,core-shell structured CdS@Gd-ZnO were prepared by chemical deposition process,which improved the carrier life and extended the visible light absorption.The details of the study and conclusions are as follows:（1）CdS@ZnO heterojunction photocatalysts with different morphologies（hexagram,rod,flower）were prepared.CZFAs had the highest degradation efficiency with a fitting constant k value of 0.063 min^–1,which was 8.3 times higher than that of ZnO.It was found that the enhanced photocatalytic performance of CZFAs was attributed to the construction of heterojunctions and the synergistic effect of nanosheets,flower-like morphology and oxygen vacancies.（2）A new three-dimensional hierarchical photocatalyst of different concentrations Gd³⁺ion-doped ZnO were prepared.The optimal photocatalytic performance when the molar ratio of Gd to Zn was 3%.approximately 63%of Rh B was degraded by GZ-3 under visible light irradiation（120 min）.The fitting constant k value of 0.0082 min^–1,which was 2.1 times higher than that of ZnO.It was found that the superior photocatalytic performance of GZ-3 originated from the smaller size of the nanosheets,the introduction of doping energy levels and finely tuned oxygen vacancy concentration.（3）The core-shell structured photocatalysts CdS@Gd-ZnO were prepared by a chemical deposition process based above part.S-scheme heterojunction CdS@Gd-ZnO was able to degrade 99.7%of Rh B(10 mg L^–1,75 min)and 95%of MB(10 mg L^–1,60 min)under visible light.It also showed high degradation of antibiotics with 93%tetracycline hydrochloride（TCH）(20 mg L^–1,60 min)and 90%oxytetracycline（OTC）(20 mg L^–1,60 min),respectively.The quasi-level kinetic fit constants k values were 0.0763 min^–1（Rh B）,0.0495 min^–1（MB）,0.0445min^–1（TCH）and 0.0393 min^–1（OTC）,which were 10.5,2.7,1.8 and 2.7 times higher than those of ZnO,respectively.It was found that the excellent photocatalytic performance of CdS@Gd-ZnO was due to the synergistic effect of the introduced doping energy levels and S-scheme heterojunctions.