Fe_3O_4@P(St-co-OBEG)核壳结构微球负载银/铂纳米粒子复合催化剂的构筑及催化性能

Preparation and Catalytic Performance of Ag/Pt Nanoparticles Catalyst Supported on Fe_3O_4@P(St-co-OBEG) Core-Shell Structured Microspheres

本工作采用无皂乳液法合成出具有核壳结构的四氧化三铁@聚(苯乙烯-co-十八醇马来酸聚乙二醇双酯)(Fe_3O_4@P(St-co-OBEG))磁性聚合物复合微球,并以此为载体制备Ag/Fe_3O_4@P(St-co-OBEG)和Pt/Fe_3O_4@P(St-co-OBEG)两种复合催化剂。借助透射电镜和动态光散射表征复合催化剂的形貌和尺寸,并通过紫外可见吸光光度法测试它们的催化性能。实验结果表明两种复合催化剂对硝基苯和4-硝基苯酚的硝基加氢还原反应均具有良好的催化性能。相比Ag/Fe_3O_4@P(St-co-OBEG),Pt/Fe_3O_4@P(St-co-OBEG)催化活性更高,这可能与Pt/Fe_3O_4@P(St-co-OBEG)催化剂中Pt纳米粒子本身的高催化活性和在磁性聚合物载体上较大的比表面积有关,还有可能归因于Pt纳米粒子在Fe_3O_4@P(St-co-OBEG)上的分布更均匀。

In this work,magnetic composite microspheres Fe3O4@P(St-co-OBEG) were prepared via a surfactant-free emulsion polymerization and were used as carriers to support Ag and Pt to obtain magnetic composite nanocatalysts.It is known that magnetic composite catalysts can not only maintain the catalytic activity of noble metal nanoparticles,but realize magnetic separation.Here,the one-step surfactant-free emulsion polymerization was achieved by using styrene (St) as hydrophobic monomers,octadecyl-butenedioate-poly(ethylene glycol)(OBEG) as surfactant and γ-Fe3O4 as magnetic particles.Besides playing a role of surfactant to stable the solution,the amphiphilic oligomer OBEG also participated in the reaction during the polymerization.In details,the Fe3O4@P(St-co-OBEG) magnetic composite microspheres were prepared by stirring the reaction mixture at 65 ℃ for 24 h under N 2 atmosphere.TEM presented a clear core-shell structure of Fe3O4@P(St-co-OBEG) microspheres.The diameter of the core were about 100-120 nm,while the thickness of the shell was in the range of 30-50 nm.Moreover,particle size analysis based on dynamic light scattering (DLS) confirmed an average particle size of about 228 nm.Subsequently,Ag/Fe3O4@P(St-co-OBEG) and Pt/Fe3O4@P(St-co-OBEG) were prepared by simply reducing AgNO 3 or H 2PtCl 6 aqueous solution with dripping NaBH 4 under room tempe-rature,and the successful deposition of Ag or Pt nanoparticles on the surfaces of Fe3O4@P(St-co-OBEG) microspheres was observed.Through catalysis tests,both Ag/Fe3O4@P(St-co-OBEG) and Pt/Fe3O4@P(St-co-OBEG) can be regarded as efficient catalysts for the reduction reactions of hydrophobic nitrobenzene and hydrophilic 4-nitrophenol,in which Pt/Fe3O4@P(St-co-OBEG) performed better in catalytic activity compared with Ag/Fe3O4@P(St-co-OBEG).This might be attributed to the more uniform distribution of Pt nanoparticles than Ag nanoparticles on the surfaces of Fe3O4@P(St-co-OBEG) microspheres according to TEM observation.