Gel Polymer Electrolyte for Direct Borohydride Fuel Cell

The electrochemistry of a direct borohydride fuel cell employing a gel polymer electrolyte was studied. Sago, a natural polymer, was employed as the polymer host for the gel polymer electrolyte. The biodegradability and low toxicity characteristics of natural polymers make them the best candidates to replace synthetic polymers as host polymers. An electrolyte composed of sago, potassium hydroxide (KOH) as reactant, and sodium borohydride (NaBH4) as fuel was prepared and evaluated as a novel gel polymer electrolyte for a direct borohydride fuel cell. An optimum composition of sago + 6 M KOH + 2 M NaBH4 gel polymer electrolyte exhibited a high ionic conductivity of 0.270 S cm-1. Based on the oxygen consumption data, it was deduced that four electrons reacted with each oxygen molecule. The performance of the direct borohydride fuel cell was assessed in terms of current-voltage, discharge and open circuit voltage. The maximum power density obtained was 8.818 mW cm-2 at a discharge capacity of ~230 mA h and a nominal voltage of 0.806 V. The Voc of the cells was about 0.900 V, which was sustained over 23 h of storage.