Water Oxidation by Cobalt Centers on Various Oxide Surfaces: The Effects of Oxide Surface Acidity and Oxygen Atom Affinity on Catalysis

Single-atom cobalt centers on various oxide surfaces (TiO₂, MgO, SBA-15, AlPO, and Y-Zeolite) were prepared and evaluated as water oxidation catalysts by photochemical water oxidation experiments. Superior catalytic rates were observed for cobalt sites on basic supporting oxides (TiO₂ and MgO) relative to those on acidic oxides (Y-Zeolite, AlPO, and SiO₂). Per-atom turnover frequencies of ca. 0.04 s^–1 were achieved, giving initial rates 100 times greater than that of a surface atom of a Co₃O₄ nanoparticle. Contrary to expectations based on theoretical work, no apparent correlation was observed between the catalytic rates and the oxygen atom affinities of the supporting oxides.