Improved hydrogen storage capacity through hydrolysis of solid NaBH_4 catalyzed with cobalt boride

摘要

In this article the feasibility of the reaction of liquid water with a solid NaBH_4/catalyst mixture for improved hydrogen storage capacity and on-demand H_2 generation is reported. The synthesized low-cost nanosized catalyst consists of a Co_2B core surrounded by an oxide layer, presenting a relatively large specific surface area (70 m~2 g~(-1)). Calorimetric experiments coupled to simultaneous measurements of the evolved hydrogen volume have shown the positive effect of the locally heat release during reduction of the superficial oxidized layer. The synergetic effects of the exothermicity of both the oxidized layer reduction and the hydrolysis reaction coupled to the high efficiency of the cobalt boride catalyst led to an "enhanced regime" observed at room temperature. The "enhanced regime" corresponds to a global reaction stoichiometry of 1 mol of NaBH_4 reacting with 3 mol of water, conducting to a hydrogen yield of 8.7 wt.%. Effects of temperature and catalyst content were studied.