Catalyst-free hydrogen generation from potassium borohydride via solvent-engineered solvolysis using a Methanol-Glycerol binary solvent system

Abstract

Catalyst-free hydrogen production from potassium borohydride (KBH4) through solvolysis under mild operating conditions is systematically investigated, with particular emphasis on the combined influence of solvent composition, reactant loading, and temperature. A binary methanol-glycerol solvent system was strategically employed to balance reaction rate enhancement and process stability. The experimental findings demonstrate that hydrogen evolution is strongly dependent on solvent ratio, where methanol-rich mixtures markedly promote reaction kinetics. The highest hydrogen generation rate, exceeding 120 mL min(-1), was achieved at an optimized methanol-to-glycerol volume ratio of 8:2, enabling complete hydrogen release (similar to 180 mL) within approximately 85 s. In comparison, single-solvent systems exhibited significantly reduced performance. Temperature-dependent studies confirmed accelerated hydrogen production at elevated temperatures, yielding an apparent activation energy of 25.5 kJ mol(-1), characteristic of a thermally controlled process. Increasing KBH4 concentration enhanced total hydrogen yield, although kinetic constraints emerged at higher loadings. Recyclability tests indicated a progressive decrease in hydrogen generation rate over consecutive runs. These results underline the effectiveness of solvent engineering combined with moderate thermal input as a sustainable and metal-free approach for efficient hydrogen generation via borohydride solvolysis.