Hydrogen generation from NaBH4 for portable proton exchange membrane fuel cell

Abstract

Sodium borohydride (NaBH₄) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells (PEMFC) because of its high theoretical hydrogen capacity. However, the slow and poor kinetic stability of hydrogen generation from NaBH₄ hydrolysis limits its application. There are two main factors influencing the kinetics stability of hydrogen generation from NaBH₄. One factor is that the alkaline by-products (NaBO₂) of the hydrolysis reaction can increase the pH of the solution, thus inhibiting the reaction process. It mainly happens in the NaBH₄ solution hydrolysis system. Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH₄ hydrolysis system. This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH₄ hydrolysis. In this perspective, we summarize the latest research progress in hydrogen generation from NaBH₄ and emphasize the design principles of catalysts for hydrogen generation from NaBH₄ solution and solid state NaBH₄. The importance of carbon as catalyst support material for NaBH₄ hydrolysis is also highlighted.