CoOx nanoparticle anchored on sulfonated-graphite as efficient water oxidation catalyst† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc01756a Click here for additional data file.

Development of efficient, robust and earth-abundant water oxidation catalysts (WOCs) is extremely desirable for water splitting by electrolysis or photocatalysis. Herein, we report cobalt oxide nanoparticles anchored on the surface of sulfonated graphite (denoted as “CoOx@G-Ph-SN”) to exhibit unexpectedly efficient water oxidation activity with a turnover frequency (TOF) of 1.2 s ; two or three orders of magnitude higher than most cobalt-based oxide WOCs reported so far. The CoOx@G-Ph-SN nanocomposite can be easily prepared by a soft hydrothermal route to have an average CoOx size below 2 nm. Additionally, the loading of CoOx@G-Ph-SN catalyst on the surface of a BiVO4 or Fe2O3 photoanode can boost remarkably the photoanode currents for robust photocatalytic water oxidation under visible light irradiation. Its excellent activity and photochemical stability for water oxidation suggest that this ultrasmall cobalt-based composite is a promising candidate for solar fuel production.