Langmuir–Hinshelwood kinetic model to capture the cobalt nanoparticles-catalyzed hydrolysis of sodium borohydride over a wide temperature range

Abstract

The present study focused on kinetics of hydrogen release through hydrolysis of sodium borohydride NaBH 4 in the presence of cobalt nanoparticles. Our experimental conditions were quite severe as we worked over the widest temperature range ever reported (i.e. 10–90 °C) and at high content of hydride (mol ratio NaBH 4/water of 9; i.e. 18.9 wt% NaBH 4 or 6.18 mol L −1). From the hydrogen evolution curves, the reaction constant versus the NaBH 4 concentration, apparent activation energy, rate constant, adsorption constant and adsorption enthalpy were determined. It was noticed that the hydrolysis kinetics depends on (i) temperature of reaction and (ii) NaBH 4 concentration. Hence, the kinetic constants were analyzed using existing kinetic models. The bimolecular Langmuir–Hinshelwood model satisfactorily captured the behavior of our catalyst consisting of cobalt nanoparticles (in our experimental conditions). Herein, the kinetic data, the kinetic model, the hydrolysis mechanism and the issues still to be addressed are reported and discussed.