Controllable Synthesis And Catalytic Performance Of Noble Metal/Conductive Polymer-Based Nanocomposites

Supported noble metal nanocatalysts exhibit good activity and selectivity for catalytic reactions in liquid phase,becoming one of the current hot spots in catalysis research.However,the noble metal nanoparticles loaded on the surface of the carrier often tend to migrate and agglomerate due to the collision between the catalysts in the liquid system.Confining the noble metal nanoparticles into the structure of the support can effectively avoid the phenomenon of migration and agglomeration,which is beneficial to enhance the stability of these noble metal nanoparticles.However,the noble metal active sites embedded in the carrier structure are often deeply buried,resulting in lower activity.Therefore,the development of noble metal-based nano-confined catalysts with both high activity and high stability is still one of the key issues in the field of liquid-phase catalysis.Therefore,in this study,noble metal nanoparticles were confined into thermally cross-linked conductive polymer containing thiophene functional groups via the physical confinement and coordination effect,to anchor the noble metal nanoparticles and ultimately enhance their stability for the liquid-phase catalytic reaction.Subsequent alkali treatment could remove the small molecules adsorbed on the surface of the noble metal nanoparticles,increasing the number of exposed active sites and enchancing catalytic activity.The specific research work is as follows:(1)Using one-step redox method,the surface of Fe3O4 nanoparticles is simultaneously coated with 3,4-ethylenedioxythiophene(PEDOT)conductive polymer and platinum palladium(Pt-Pd)two-component noble metal nanoparticles.The composite shell layer is then thermally crosslinked and alkali treated to obtain Fe3O4@TC-PEDOT/Pt-Pd(Alkali)nanocomposites.The two-component noble metal nanoparticles are highly uniformly dispersed into the thermally crosslinked polymer shell.The physical confinement and coordination effect of the conductive polymer containing thiophene functional group on the noble metal nanoparticles can prevent them from collision and even deactivation during the catalytic processes.The small molecules,generated during the heat treatment process,adsorbed on the surface of the precious metal nanoparticles could be removed by alkaline treatment..The catalysts show good catalytic activity and excellent cycle stability towards the hydrogenation of aromatic nitro compounds,and at the same time the inner core also endows the catalyst with good magnetic recovery.(2)Based on the above research,it is proposed to deposit a layer of ultra-thin PEDOT conductive polymer composite shell with highly dispersed Pd noble metal nanoparticles on the surface of core-shell structure Fe3O4@Si O2,and hydrogen peroxide(H2O2)is used to control the degree of polymerization and to enhance the stability of the composite shell.After heat treatment at 300?,the conductive polymer shell is further cross-linked,and then the middle Si O2 shell is removed by alkali treatment to obtain thermally cross-linked Fe3O4@void@TC-PEDOT/Pd nanocomposite catalytic material.The as-prepared Pd nanoparticles have a uniform particle size distribution with the average size of about3.04±0.34 nm.Besides the dual anchoring of physical confinement and coordination effect,the collision probability between the substrate and noble metal nanoparticles is enhanced through the bidirectional diffusion of the substrate inside and outside the ultrathin shell,and catalytic activity of this catalyst is further improved while maintaining stability.The catalysts also show good catalytic activity and excellent cycle stability towards the hydrogenation of aromatic nitro compounds.