Studies On The In-situ Growth And Catalytic Activity Of Gold And Platinum Nanoparticles On The Surface Of Silica Microspheres

In recent years,noble metal nanoparticles have been widely used in the field of catalysis due to their unique photoelectric,catalytic and electromagnetic properties.Among them,noble metal nanocatalysts exhibit high selectivity and catalytic activity in catalytic reduction reactions,and thus have attracted much attention.In this paper,platinum,gold and silver nanoparticles supported by SiO2nanospheres were prepared by in-situ growth of platinum and gold nanoparticles by novel silica microspheres,and used for catalytic experiments.Detailed research is carried out by XPS,TEM,SEM,UV-Vis and other technologies.The catalytic properties of platinum and gold nanoparticles were studied by catalytic nitrobenzene reduction of aniline and styrene epoxidation.The UV-visible spectrophotometer monitors the catalytic process in real time.The synthesis process of silica microsphere-loaded gold nanoparticles AuNPs?<1nm?and its application in controlling the conversion and selectivity of styrene epoxidation were introduced.The Ag nanoparticles?AgNPs?were used as the sacrificial template to deposit the surfactant-free Au nanoparticles on the SiO₂microspheres by electro-coupling reaction.The supported catalyst AuNPs/SiO₂ was prepared directly,and the crystal faces were exposed without post-treatment..Using H₂O₂ as oxidant and ethanol as solvent,the reaction conversion rate was 46.7%and the selectivity was 91.7%.This study not only provides an active,recyclable catalyst for green oxidants and solvent oxidized styrene,but also demonstrates the ability of sulfhydryl-modified silica microspheres to stabilize precious metal nanoparticles without any surfactant.A simple and practical aqueous phase reduction method was designed to grow in situ on the surface of silica nanospheres to synthesize platinum nanoparticles with high catalytic performance?PtNPs@SiO₂?,and the products were characterized by a series of instruments.The results show that the platinum nanoparticles are supported on the surface of the silica microspheres,have good growth,uniform particle size,small size,no agglomeration,and are not easy to fall off and have no ligand.The conversion of p-nitrophenol?4-NP?to p-aminophenol?4-AP?was catalyzed by platinum nanoparticles.The results showed that the rate of reduction of 4-NP by reducing agent was significantly accelerated after the addition of PtNPs@SiO₂catalyst.The dosage and the amount of reducing agent,the color of p-nitrophenol gradually fades,the solution changes from light yellow to colorless,which shows that it has good repeatability and high catalytic activity.It can be recycled and recycled many times,which is of great significance to green catalyst.