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

Abstract

This paper introduces and discusses the latest research on the use of H 2 generated via the NaBH 4 hydrolysis reaction for proton exchange membrane fuel cells (PEMFCs). To realize the NaBH 4–PEMFC system, many hydrolysis catalysts such as Ru/anion-exchange resins, Pt/LiCoO 2, Co powder/Ni foam, PtRu/LiCoO 2 and Ru/carbon have been proposed. Through these efforts, the hydrolysis reaction conversion approached 100%. In addition, the average H 2 generation rate based on most of the reports generally ranged from 0.1 to 2.8 H 2 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 H 2 generation rate was 28 H 2 l min − 1 g − 1 (catalyst) with the catalyst of Pt/carbon (acetylene black). Considering these reports and the advantageous features of NaBH 4 hydrolysis, the NaBH 4–PEMFC system seems to be technologically feasible and would constitute an alternative system of supplying H 2 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 NaBH 4 were to be further reduced, this system could become the most powerful competitor in portable application fields of PEMFC.