Optimization of Hydrogen Generation by Catalytic Hydrolysis of NaBH4 with Halloysite-Supported CoB Catalyst Using Response Surface Methodology

Abstract The hydrolysis of sodium borohydride (NaBH4) is a promising reaction with a possible practical application as a means of generating hydrogen. The efficiency of hydrogen production can be enhanced significantly by use of a catalyst during the reaction. Cobalt borides show significant catalytic activity, but unsupported CoB particles aggregate easily and are difficult to separate from the reaction medium for re-use. The objectives of the present study were to use halloysite (Hly) as a support material to increase the catalytic activity and reusability of a Co metal-based system and to investigate the binary effect of metal loading and reaction parameters on the hydrolysis of NaBH4. Catalysts were prepared by wet impregnation and chemical reduction. The surface morphology and structural properties of the prepared catalysts were characterized using N2 adsorption-desorption and the Brunauer-Emmet-Teller (BET) method, field emission scanning electron microscopy (FE-SEM), with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS). Response surface methodology (RSM) was used to optimize metal loading and reaction conditions for the hydrogen-generation rate. Optimum reaction conditions were determined (using Design Expert 7.0 software) as 5.01 wt.% Co loading using a Co-B/Hly-supported catalyst, 0.44 M NaBH4, 10.66 mg catalyst, and at a reaction temperature of 39.96°C. The maximum hydrogen generation rate was 33,854 mL min−1 gCo−1 under these conditions.