One- or Two-Electron Water Oxidation, Hydroxyl Radical, or H2O2 Evolution

Electrochemical or photoelectrochemcial oxidation of water to form hydrogen peroxide (H2O2) or hydroxyl radicals ((OH)-O-center dot) offers a very attractive route to water disinfection, and the first process could be the basis for a clean way to produce hydrogen peroxide. A major obstacle in the development of effective catalysts for these reactions is that the electrocatalyst must suppress the thermodynamically favored four-electron pathway leading to O-2 evolution. We develop a thermochemical picture of the catalyst properties that determine selectivity toward the one, two, and four electron processes leading to (OH)-O-center dot, H2O2, and O-2.