Transition Metal Modified Photocatalytic Materials For Selective Oxidation And Anti-oxidation

The un-renewability of fossil energy and the unavoidable environmental pollution problems during utilization are becoming increasingly severe.The efficient use of solar energy is an important direction of current research.Building an efficient photocatalyst is the key to solar energy utilization.Photocatalytic materials generally have problems such as weak visible light absorption capacity and serious photo-generated electron-hole recombination,which limit their photocatalytic activity.With the help of metal doping strategies,transition metals such as Co,Cu,Zn,etc.have been successfully introduced into g-C₃N₄,ZnO and carbon dot materials to improve electron transport efficiency and be used in the fields of photocatalytic styrene epoxidation and photocatalytic active oxygen elimination,the main research contents are as follows.（1）The Cu@CN material was prepared,using visible light as the light source,successfully achieved rapid photocatalytic epoxidation of styrene under mild conditions.Through the Na BH₄ reduction strategy of Cu ions,Cu-Cu₂O was successfully loaded on g-C₃N₄（Cu@CN）.Cu₂O and g-C₃N₄ form a p-n junction,which greatly improves the visible light absorption and electron transport capabilities of Cu@CN,and reduces the photo-generated electron-hole recombination rate.Cu@CN was applied to photocatalytic epoxidation of styrene,the results show that 10-Cu@CN（Cu content 10 wt%）has the best reactivity.After reacting at room temperature and normal pressure for 4 hours,the conversion,selectivity and yield of styrene epoxidation reached 91.3%,75.8%and 69.2%.Compared with commonly reported severe reaction conditions such as high temperature,this reaction is gentler and more controllable,and the catalyst preparation is simple.（2）The Co/ZnO material was prepared,using oxygen as the oxidant and low-power LED lamp as the light source to achieve the photocatalytic epoxidation of styrene under mild conditions.A simple co-precipitation strategy was used to prepare Co-doped ZnO materials（Co/ZnO）.XRD and other characterization methods proved that Co was incorporated into the ZnO lattice and formed a local splitting energy level,which effectively reduced the band gap of ZnO and promoted the separation and transport of photogenerated electrons and holes.Applying Co/ZnO to the photocatalytic epoxidation of styrene,40-Co/ZnO has the best catalytic activity.The results showed that the styrene conversion rate reached 65.1%,the selectivity of styrene oxide reached 66.8%,and the yield reached 43.5%at room temperature and normal pressure for 24 hours,which is close to the oxidation achieved by thermal catalysis at 140℃in literature reports.72%selectivity for styrene.（3）Prepared Cu Zn-CDs and achieved high-efficiency photocatalytic elimination of O₂^·-and H₂O₂.Calcined with EDTA metal salt and Na Cl as raw materials,transition metal doped carbon dots were prepared.Compared with pure CDs,Cu Zn-CDs exhibits excellent salt resistance,acid and alkali resistance,heat resistance and storage stability,as well as stronger electron transport capabilities.Cu Zn-CDs is applied to the elimination of photocatalytic reactive oxygen species,and its reaction activity is equivalent to that of natural SOD enzyme and CAT enzyme.Studies have shown that the Cu Zn metal doping center is the active site for eliminating active oxygen.DFT calculations prove that the presence of Cu balances the positive charge of Zn and increases the electron cloud density of Zn sites,thereby achieving antioxidant activity under acidic conditions.Cu Zn-CDs has the application prospects as a substitute for bifunctional enzymes.