Deposition of small amts. of IrO2 clusters on the B-doped diamond (BDD) surface (BDD-IrO2 electrode) dramatically enhances both the O2 evolution reaction and the oxidn. of orgs. in the potential region of water decompn. The fact that BDD-IrO2 electrode behaves similarly to IrO2-DSA type electrodes suggests that the IrO2 clusters on the BDD surface act as redox catalysts in both oxygen evolution and orgs. oxidn. [on SciFinder (R)]