New catalysts for borohydride electro-oxidation using Rh porphyrins

New borohydride electro-oxidation catalysts for direct borohydride fuel cells were developed. These catalysts use rhodium porphyrins on carbon black. The overpotential for borohydride electro-oxidation is much lower than that for a gold electrode. Hydrogen generation by the hydrolysis of borohydride is suppressed much more with rhodium porphyrin catalysts than with a platinum catalyst. Rh porphyrins oxidized borohydride below 0 V vs. a reversible hydrogen electrode. The measurement of hydrogen generation after electrolysis indicates that the apparent number of electrons transferred in rhodium octaethylporphyrin exceeds 7.