We have prepared the amphiphilic molecular catalyst [Co-III(L-OC18)(pyrr)(2)]ClO4 (1), where L-OC18 is the deprotonated form of N,N'-[4,5-bis(octadecyloxy)-1,2-phenylene]dipicolinamide. Species 1 can be anchored onto a carbon black support to yield the assembly 1@CB, which can catalyze water oxidation at an affordable onset overpotential of 0.32 V, with a current density of 10 mA/cm(2) at 0.37 V. Moreover, 1@CB displays TOF = 3850 h(-1). A mechanism is proposed based on the experimental and density-functional-theory-calculated data.