Enhanced catalytic properties of Fe3O4/Ag magnetic microspheres synthesized by a novel thermal co-reduction method

In this report, a highly dispersity and smaller size of Ag nanoparticles were directly embedded into/onto the hollow-porous Fe3O4 magnetic microspheres (Fe3O4/Ag MMPs) by a novel thermal co-reduction method, which used both NaBH4 and trisodium citrate dihydrate as reducing agent to reduce the AgNO3 to Ag nanoparticles. The structural, morphological and magnetic properties of the obtained Fe3O4 and Fe3O4/Ag MMPs were characterized by various techniques, including FT-IR, XRD, XPS, FE-SEM, TEM, VSM and so on. The catalytic performance of Fe3O4/Ag MMPs was examined towards the reduction of p-nitroaniline into p-phenylenediamine in fresh NaBH4 solution, which employing UV-vis spectrophotometer at 380 nm to continuously monitor the reaction progress. The characterization and experimental results indicated that Ag nanoparticles were successfully anchored both in the inner and outer of the hollow-porous Fe3O4 magnetic supports with a weight percent of 31.33%, in addition, the Fe3O4/Ag MMPs remained a high saturation magnetization value of 50.53 emu/g. More importantly, Fe3O4/Ag MMPs had excellent catalytic reduction properties, which fitted well with the first-order kinetics equation and the corresponding apparent rate constant k was 0.45 min(-1). The enhanced catalytic properties of Fe3O4/Ag MMPs may be ascribed to the numerous loading of Ag nanoparticles, which were highly monodispersed and stable in an aqueous solution, as well as the remarkable synergistic effect between Ag nanoparticles and hollow-porous Fe3O4 magnetic microspheres.