Dual-Templated Cobalt Oxide for Photochemical Water Oxidation

Mesoporous Co₃O₄ was prepared using a dual templating approach whereby mesopores inside SiO₂ nanospheres, as well as the void spaces between the nanospheres, were used as templates. The effect of calcination temperature on the crystallinity, morphology, and textural parameters of the Co₃O₄ replica was investigated. The catalytic activity of Co₃O₄ for photochemical water oxidation in a [Ru(bpy)₃]²⁺[S₂O₈]^2- system was evaluated. The Co₃O₄ replica calcined at the lowest temperature (150°C) exhibited the best performance as a result of the unique nanostructure and high surface area arising from the dual templating. The performance of Co₃O₄ with highest surface area was further examined in electrochemical water oxidation. Superior activity over high temperature counterpart and decent stability was observed. Furthermore, CoO with identical morphology was prepared from Co₃O₄ using an ethanol reduction method and a higher turnover-frequency number for photochemical water oxidation was obtained.