We have found that certain kind of complexes on carbon black catalyze borohydride electro-oxidation. All of the Rh porphyrins tested in this study exhibited high activity regardless of the structure of the porphyrin ligands. While other metalloporphyrins also catalyzed borohydride electro-oxidation, the activities were much lower than those of Rh porphyrins. Even Rh tetrakis(4-methylphenyl)porphyrin, which exhibited the highest activity, scarcely catalyzed the chemical decomposition of borohydride under open-circuit conditions. These metalloporphyrin-based catalysts tested do not promote H(2) electro-oxidation. Other Rh complexes (Rh(2)Cl(2)(CO)(4) and Rh phthalocyanin) also catalyze borohydride electro-oxidation. Rh(2)Cl(2)(CO)(4) oxidizes borohydride at lower potentials than Rh porphyrins; it can catalyze borohydride even below 0 V vs. RHE. A one-compartment H(2)-generator that also generates electric power was constructed using Rh(2)Cl(2)(CO)(4) as an anode catalyst. (C) 2011 Elsevier B.V. All rights reserved.