Investigation On The Synthesis And Photocatalytic Performance Of Au And Ag Nanoclusters Catalysts

In recent years,Au and Ag nanoclusters have become a research focus due to their ultra-small size and unique optical properties.Noble metal nanoclusters were a type of molecular aggregates composed of several to hundreds of metal atoms,the size of which is between a single metal atom and a larger metal nanoparticle.Au and Ag nanoclusters had a quantum size effect.Their discrete HOMO-LUMO energy levels were consistent with the properties of narrow-bandgap semiconductors and had a high response to visible light,so they exhibited photocatalytic behavior.The existing literature reported that the application of Au and Ag nanoclusters catalysts was limited by the photocatalytic activity and stability.Therefore,how to prepare noble metal nanocluster catalysts with good stability and high catalytic activity was still an urgent problem to be solved.In this paper,Au nanoclusters?AuNC?and Ag nanoclusters?AgNC?were synthesized by size focusing methods respectively,and different schemes were used to stabilize nanoclusters.On this basis,the catalytic activities of Au nanoclusters and Ag nanoclusters were investigated respectively.The specific work was as follows:Ultrasmall Au nanoclusters?AuNC?and ultrathin BiOCl nanosheets were prepared.The size of AuNC was concentrated at 1.0 nm,and the thickness of BiOCl nanosheets was 2.6 nm.The two were compounded by constructing a heterojunction,which improves the stability of Au nanoclusters and the photocatalytic activity of the composite material.The newly prepared AuNC/BiOCl exhibited excellent catalytic performance for benzylamine,whose TOF value was as high as 1916 h^-1,and it had high selectivity?99%?for other amine conversions,which proves its good universality to amine oxidation.During the research,it was found that the content and structural integrity of AuNC,as well as the thickness and PVP content of BiOCl nanosheets,were all factors that affect the photocatalytic activity of AuNC/BiOCl.Moreover,the AuNC/BiOCl composite had good photostability,and the catalytic activity did not decrease significantly after 5 cycles.The experimental results proved that electron?e^-?and superoxide radical?·O₂^-?were the main active substances in the AuNC/BiOCl reaction process,and the reaction mainly undergoes a carbocation intermediate process.The excellent catalytic activity of AuNC/BiOCl was studied,and it was found that it was mainly attributed to the construction of"type II heterojunction".Ag nanoclusters?AgNC?were synthesized with the same ligands,and AgNC/P25 catalysts were prepared by utilizing the characteristics of the interaction of AgNC silicone grease bonds with the hydroxyl groups on the surface of TiO₂?P25?.The photocatalytic degradation effect of AgNC/P25 composite material on methyl orange?MO?under 5 W blue?455 nm?LED lamp reached 99.2%,and its degradation rates were 14 and 19 times that of P25 and Ag NP/P25,respectively.In addition,in terms of simultaneous degradation of dual pollutants,AgNC/P25 also showed higher activity.The reaction rate of the dual pollutant system was higher than that of the single system,mainly due to the redox reaction consumes a lot of electrons and holes,which makes the reaction rate increases.Thereby further improved the separation efficiency of its electrons and holes,so that the reaction rate was increased.AgNC/P25 had a removal rate of more than 90%for MO/Cr???,phenol/Cr???,and4-chlorophenol/Cr???mixed systems.The composite had high cycle stability and good degradation effect after 5 cycles.The research found that the main active substances in the photocatalytic degradation process were holes?h⁺?and superoxide radicals?·O₂^-?.