Catalytic activity of core–shell structured Cu/Fe3O4@SiO2 microsphere catalysts

The core–shell structured Cu/Fe3O4@SiO2 catalysts were prepared via two steps. First, the Fe3O4@SiO2 microspheres were synthesized using the nano-Fe3O4 as the core, TEOS as silica source, and CTAB as surfactant. Second, the Cu nano-grains, obtained by reducing copper ammonia complexes with hydrazine hydrate, were supported on the surface of the Fe3O4@SiO2 microspheres. The structure of the samples was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms and vibration sample magnetometer (VSM). The catalytic activity of Cu/Fe3O4@SiO2 catalysts for the production of hydrogen from low concentration formaldehyde solution was evaluated. The results indicated that the size of the Fe3O4@SiO2 and the Cu/Fe3O4@SiO2 was about 500 nm. The diameter of Cu particles on the surface of Cu/Fe3O4@SiO2 was 10 nm. Both the Fe3O4@SiO2 and the Cu/Fe3O4@SiO2 had the mesoporous structure. The samples presented the superparamagnetism at room temperature. The low concentration formaldehyde could be effectively converted into hydrogen at room temperature. The Cu/Fe3O4@SiO2 with Cu content 15 wt% exhibited the best catalytic performance. The accumulative amount of H2 reached 42 mL in 45 min. After reaction recycling for 8 times, the catalytic activity of the catalyst had not been obviously dropped.