Preparation Of ZnCr-LDHs/Bi₂MoO₆ Composite Material And Its Photocatalytic Performance

Hydrotalcite（LDH）and hydrotalcitc-like compounds（LDHs）are layered double metal hydroxides composed of positively charged metal hydroxide layers and interlayer anions.As functional material s,they arc simple to prepare and have unique characteristics.The layered structure and performance arc widely used in the field of water treatment.When the hydrotalcite layer contains Zn,Cr,Ti,Cu,Ni and other metal elements,it has the properties of semiconductor photocatalysis.ZnCr hydrotalcite-like compounds（ZnCr-LDHs）is widely used in photocatalytic fields such as the production of H2,O2 and the degradation of organic wastewater due to its high photosensitivity,quantum yield and stability.However,ZnCr-LDHs is produced by light the electron-hole pairs are easy to recombine,resulting in low photon utilization efficiency.Therefore,in this paper,ZnCr-LDHs and Bi₂MoO₆ are combined to form a "Z-type" heterojunction to avoid the rapid recombination of electron-hole pairs and prepare ZnCr-LDHs/Bi₂MoO₆ composite material,and then combined with NCQDs to improve the electron transfer efficiency to prepare NCQDs/ZnCr-LDHs/Bi₂MoO₆ composite photocatalyst with better photocatalytic performance,which was characterized by XRD、BRT、SEM、UV-vis DRS、XPS、PL and other technologies,and used Rhodamine B B（RhB）and tetracycline hydrochlo ride（TC）are the target pollutants,their photocatalytic performance was investigated.The specific research results are as follows:The ZnCr-LDHs/Bi₂MoO₆ composite photocatalyst was prepared by the co-precipitation method,which has a good crystal form and successfully recombined,the formed heterojunction inhibits the recombination of photogenerated electron-hole pairs;The NCQDs/ZnCr-LDHs/Bi₂MoO₆ catalyst was synthesized by impregnation method,it is found that NCQDs are uniformLy dispersed on the ZnCr-LDHs/Bi₂MoO₆ material,and the formed catalyst still maintains the original crystal structure,NCQDs with upconversion properties act as electron acceptors,and the electron transfer between ZnCr-LDHs/Bi₂MoO₆ increases their photocatalytic activity.The prepared ZnCr-LDHs/Bi₂MoO₆ exhibits high photocatalytic activity when the compound ratio of ZnCr-LDHs and Bi₂MoO₆ is 3:1.When the pH is 7,the dosage is 40mg,and the initial concentration of RhB is 10mg/L,the removal rate of RhB at 100min is 94.71%,it is 4.09 times that of ZnCr-LDHs and 2.93 times that of Bi₂MoO₆,which greatly improves the photocatalytic performance.After NCQDs are loaded on ZnCr-LDHs/Bi₂MoO₆,it shows better photocatalytic activity.When the NCQDs load is 2mL,pH is 7,the dosage is 30mg,and the initial concentration of RhB is 10mg/L,the effect of RhB on RhB is The removal rate reached 99.58%,and the removal rate of TC was 98.86%.The active free radicals that play a major role in the process are ·O2-and h+,and it is found in the cycle experiment that the obtained two catalysts have good reusability and stability.