Sodium borohydride as the hydrogen supplier for proton exchange membrane fuel cell systems

This paper introduces and discusses the latest research on the use of H₂ generated via the NaBH₄ hydrolysis reaction for proton exchange membrane fuel cells (PEMFCs). To realize the NaBH₄-PEMFC system, many hydrolysis catalysts such as Ru/anion-exchange resins, Pt/LiCoO₂, Co powder/Ni foam, PtRu/LiCoO₂ and Ru/carbon have been proposed. Through these efforts, the hydrolysis reaction conversion approached 100%. In addition, the average H₂ generation rate based on most of the reports generally ranged from 0.1 to 2.8 H₂ l min^{- 1} g^{- 1} (catalyst), which produced a level of PEMFC performance equivalent to 0.1-0.3 kW g^{- 1} (catalyst). However, it was also reported that the H₂ generation rate was 28 H₂ l min^{- 1} g^{- 1} (catalyst) with the catalyst of Pt/carbon (acetylene black). Considering these reports and the advantageous features of NaBH₄ hydrolysis, the NaBH₄-PEMFC system seems to be technologically feasible and would constitute an alternative system of supplying H₂ in fuel cells. However, some challenges remain, such as the deactivation of the catalyst, the treatment of the by-products, and the proper control of the reaction rate. In addition, if the price of NaBH₄ were to be further reduced, this system could become the most powerful competitor in portable application fields of PEMFC.