Influences of fuel crossover on cathode performance in a micro borohydride fuel cell

Influences of borohydride crossover on cathode performance were studied in a micro direct borohydride fuel cell (DBFC). The results showed that fuel crossover resulted in decreases in open circuit potentials of cathodes. On the other hand, effects of fuel crossover on cathode overpotentials strongly depended on the cathode material. The Pt/C cathode demonstrated a small potential drop of 0.11 V, while the Ag/C cathode had a much larger potential drop of 0.26 V under the same condition. Fuel crossover was found to be depressed during current operations. It is possible that fuel depletion happened around the anode during operation, resulting in a decrease of fuel concentration gradient across the membrane and thus less crossover. Experiments also showed that a balance in wet-proof property is essential for the cathode in the direct borohydride fuel cell and the stability of cell performance was mainly dependent on wet-proof durability of the cathode.