CoO-Co_2P composite nanosheets as highly active catalysts for sodium borohydride hydrolysis to generate hydrogen

摘要

In this paper, CoO-Co2P composite nanocatalysts as highly active catalysts were successfully prepared for catalytic hydrolysis of sodium borohydride (NaBH4) to generate hydrogen. For catalyst preparation, pre-synthesized Co(OH)(2) nanosheets were uniformly mixed with sodium hypophosphite (NaH2PO2) and then treated through vapor-phase phosphorization process. For characterization, field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), N-2 adsorption-desorption measurement and X-ray photoelectric spectroscopy (XPS) were carried out, and traditional water-displacement method was performed to measure the hydrogen generation rate (HGR). It was found that component and catalytic activity of the composites were greatly affected by the ratio of Co(OH)(2) to NaH2PO2. When the ratio was 2:1, the obtained catalyst composed of CoO and Co2P presented the highest HGR up to 3.94 L min(-1) g(-1) using a 2 wt.% NaBH4 + 8 wt.% NaOH solution at 25 degrees C, and the apparent activation energy was detected as low as 27.4 kJ mol(-1) . Additionally, the optimum CoO-Co2P catalyst still retains 60% of the initial activity after recycling four times.