Water oxidation catalyzed by cobalt(II) adsorbed on silica nanoparticles

A novel, highly efficient, and stable water oxidation catalyst was prepared by a pH-controlled adsorption of Co(II) on ∼10 nm diameter silica nanoparticles. A lower limit of ∼300 s ^-1 per cobalt atom for the catalyst turnover frequency in oxygen evolution was estimated, which attests to a very high catalytic activity. Electron microscopy revealed that cobalt is adsorbed on the SiO ₂ nanoparticle surfaces as small (1-2 nm) clusters of Co(OH) ₂. This catalyst is optically transparent over the entire UV-vis range and is thus suitable for mechanistic investigations by time-resolved spectroscopic techniques.