Controllable Synthesis And Catalytic Performance Of Metal Atom Site Catalysts Supported By Inorganic Semiconductor Materials

The development of low-cost,high-performance photocatalysts at the atomic level has become a challenging challenge for large-scale applications of renewable clean energy technologies.Atomic site photocatalysts with nearly 100%atomic utilization,well-defined structures and excellent performance have received much attention from the scientific community.When the size of metal catalytic sites is reduced to a single atom,the surface energy of metal atoms increases dramatically,which poses a challenge to the stability of the material;on the other hand,the lack of reported means to modulate the performance of atomic site photocatalysts is detrimental to their further applications.To address the above problems,this thesis develops three new materials of atomic site photocatalysts loaded on inorganic semiconductor materials by means of photoreduction strategy and diatomic strategy,and explores the relationship between material structure and catalytic performance by using benzylamine oxidation,nitrogen alkylation reaction and benzyl alcohol C-C coupling as model reactions.The following results were obtained.(1)An atomic site catalyst for efficient photocatalytic oxidation of benzylamine was developed using an oxygen-deficient strategy.Bismuth nitrate and potassium bromide were used as precursors to synthesize BiOBr carriers with oxygen defects using a solvothermal reaction.Then Ru metal elements were loaded on the BiOBr carriers by impregnation photoreduction,and the nanoflower structured BiOBr-loaded Ru atomic site photocatalysts(Ru/BiOBr)with high specific surface area were successfully prepared.The catalytic results showed that in the oxidation of benzylamine to benzonitrile with tert-butyl hydroperoxide as the oxidant,the atomic site catalyst Ru/BiOBr exhibited up to 100%conversion of the substrate benzylamine and 99%catalytic selectivity for the selective generation of benzonitrile,which far exceeded the comparison samples Ru nanoparticles/BiOBr and BiOBr.(2)An efficient catalytic photocatalyst for nitrogen alkylation reaction was developed using a bimetallic site-modulation strategy.Using cadmium nitrate and thiourea as precursors,a rod-like CdS carrier was synthesized by a solvothermal reaction.Then,In/CdS was obtained by loading In metal on the surface of CdS through the solvothermal method.further,Bi metal was loaded on In/CdS by impregnation photoreduction method,and Bi,In bimetallic site photocatalyst(BiIn/CdS)loaded on CdS nanorods was successfully prepared.The catalytic results showed that in the coupling reaction of aniline with benzyl alcohol,BiIn/CdS induced the conversion of aniline up to 92.3%under light induction and produced nitrogen alkylation products with a selectivity of 93.5%,which was much better than other comparative sample catalysts.(3)An efficient photocatalyst for direct C-C coupling of benzyl alcohol was developed using a sulfur atom-anchored metal atom site strategy.The catalysts loaded with Pt on In2S3 nanosheets(Pt/In2S3)were successfully prepared by solvothermal and photo-induced reduction using indium nitrate and thiosemicarbazone as precursors.It was tentatively demonstrated by high-resolution transmission electron microscopy that Pt elements on In2S3 nanosheets were free of metal particles and clusters aggregation.The catalytic results showed that the Pt/In2S3 catalyst exhibited high catalytic activity in the direct C-C coupling reaction of benzyl alcohol catalyzed by photoinduction at room temperature,and the conversion of benzyl alcohol reached 95.5%,which was superior to In2S3 and Pt nanoparticles/In2S3 comparative catalysts.