Direct borohydride fuel cells (DBFCs)

Abstract

Direct borohydride fuel cells (DBFCs) operate with sodium borohydride as a fuel and oxygen or hydrogen peroxide as the oxidant. These fuel cells offer advantages over similar types of fuel cells in terms of higher open-circuit voltage and energy density. These benefits originate from the direct oxidation of borohydride that proceeds with the transfer of eight electrons. Still, this number is lower in practice due to the borohydride hydrolysis taking place in parallel. Problems arise on the cathode side as the sluggish oxygen reduction can proceed as a preferable four-electron process or as a two-electron process. In the case of hydrogen peroxide as the oxidant, its decomposition also lowers the cell performance. This chapter summarizes the efforts made in the search for anode and cathode materials with high activity and stability to lead to optimum DBFC performance. The influence of fuel cell components, such as membrane separators and cell operation parameters are also briefly overviewed.