Preparation of CoB/ZIF-8 supported catalyst by single step reduction and its activity in hydrogen production

Abstract

CoB/ZIF-8 supported catalysts were successfully prepared using Co/Zn-ZIF-8 as the precursor by single-step reduction, which was applied in hydrogen release from the hydrolysis of NaBH4. Reducible Co ions of Co/Zn-ZIF-8 can be partially in-situ transformed into CoB by direct reduction, whereas ZIF-8 framework structure can be well preserved due to the resistance of Zn to reducing ambiences. Accordingly, CoB active components can be highly loaded onto ZIF-8 support to produce CoB/ZIF-8 catalysts. The texture evolution of Co/Zn-ZIF-8 during reduction was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscope and nitrogen adsorption–desorption isotherms. Compared with the reduction of Co-ZIF-67, the framework structure of Co/Zn-ZIF-8 can be effectively preserved although Co ions of Co/Zn-ZIF-8 were partially reduced into cobalt-based alloy. In the hydrogen release from hydrolysis of NaBH4, CoB/ZIF-8 supported catalyst exhibits excellent catalytic activity. The effect of NaOH concentration, NaBH4 concentration and reaction temperature on hydrolysis reaction of NaBH4 was deeply studied based on this catalyst. Compared with other published catalysts, this catalyst exhibits relatively low activation energy of about 57.72 kJ mol−1.