Effects of acid accelerators on hydrogen generation from solid sodium borohydride using small scale devices

This work describes hydrogen generation using a heterogeneous chemical system for small scale portable applications. Hydrogen generation using acidified water and solid sodium borohydride (NaBH4) is presented. The effects of two modes of contacts – (1) a flow through type and (2) a diffusion type – contact in a 5 mm3 device are discussed. The effects of contacting several mineral and benign acids with NaBH4 are compared by monitoring hydrogen yield. Among the mineral acids examined, HCl generates a maximum hydrogen yield of 97% of the theoretical yield at 3N concentration. The benign acids are required in higher concentration compared to mineral acids. Formic acid produces 87% of the hydrogen yield at 12N. The products of the reaction have been characterized using scanning electron microscopy and X-ray diffraction. A combination of acid strength, porosity of the interface, and solubility of the byproducts contributes to the different hydrogen yields in the presence of various acids.