Depression of hydrogen evolution during operation of a direct borohydride fuel cell

Hydrogen evolution from the anode usually occurs during operation of a Direct Borohydride Fuel Cell (DBFC). This would not only decrease the fuel utilization, but also lower the cell performance because hydrogen bubbles would hinder ion movement in the anolyte. In this paper, the hydrogen evolution behavior is investigated based on relations of hydrogen evolution rates versus operation currents of the DBFC. The effects of anode modification on the hydrogen evolution rate and the cell performance were investigated. It was found that hydrogen evolution was depressed by adding Pd, Ag and Au catalysts in the anode. Coating a thin Nafion film on the catalyst surfaces was another effective way to decrease the hydrogen evolution rate. Depression of the hydrogen evolution and improvement of the DBFC performance can be achieved by adding carbon supported Pd in Ni anode with a suitable content of Nafion. However, too much Nafion in the anode would degrade the DBFC performance.