Controllable Synthesis And Catalytic Properties Of Magnetic Core-shell Catalysts With Spatially Confined Pt Nanoparticles

Magnetic catalysts with spatially confined noble metal nanoparticles exhibit good stability,moderate catalytic activity and magnetic recoverability,have been being one of the most potential catalysts in liquid phase systems.However,the poor compatibility among magnetic inorganic core,shell materials,and noble metal nanoparticles hinders to obtain small noble metal nanoparticles with high dispersity,which suppresses their activities.Therefore,it is still a challenge to improve the compatibility among magnetic inorganic core,shell materials,and noble metal nanoparticles and to develop high-efficiency magnetic catalysts with spatially confined noble metal nanoparticles.First,a combined strategy,self-templated dissolution-induced deposition and subsequent pyrolysis,was proposed to synthesize magnetic catalysts with spatially confined Pt nanoparticles.Firstly,3,4-ethylene dioxythiophene（EDOT）monomers were oxidated simultanesously by both K₂PtCl₄ and Fe³⁺,released from acid-induced dissolution of Fe₃O₄ nanoparticles,to obtain core-shell Fe₃O₄@PEDOT/Pt precursor.After heat treatment and alkali treatment of the precursor,the core-shell alkali-treated Fe₃O₄@thermally treated PEDOT/Pt（Fe₃O₄@TT-PEDOT/Pt（Alkali））catalyst was synthesized.The small platinum nanoparticles are uniformly confined in the TT-PEDOT shell structure,which enhances atom utilization and catalytic activity of Pt nanoparticles;and the thermally cross-linked PEDOT shell structure limits the migration and agglomeration of these small Pt nanoparticles and enhances structural stability of the catalyst in the catalytic processes.As expected,the catalyst exhibits good activity and stability towards the reduction reaction of aromatic nitro-compounds.Secondly,another combined strategy,controllable self-templated dissolution-induced deposition and subsequent pyrolysis,was proposed to prepare magnetic catalysts with smaller and spatially confined Pt nanoparticles.Firstly,EDOT monomers were oxidated at an appropriate rate simultaneously by both K₂PtCl₄ and Fe³⁺,released controllably from controlled dissolution of Fe₃O₄ nanoparticles with an addition of acid at a certain feed rate,to obtain core-shell Fe₃O₄@PEDOT/Pt precursor with smaller Pt nanoparticles.After heat treatment and alkali treatment of the precursor,the core-shell alkali-treated Fe₃O₄@thermally treated PEDOT/Pt（Fe₃O₄@TT-PEDOT/Pt（Alkali））catalyst was synthesized.By precisely controlling the redox rate among EDOT,K₂PtCl₄ and Fe³⁺,homogenous polymer shell high dispersity of noble metal nanoparticles into the shell were achieved.More importantly,the aim to obtain smaller Pt nanoparticles with narrow distribution confined into the PEDOT shell was also achieved.As expected,smaller particle size with more exposed active sites ensure higher activity and stability of the catalyst with regard to the reduction reaction of the aromatic nitro-compounds.