CH₄ Synthesis from CO₂ and H₂O of an Electron Source over Rh-Ru Cocatalysts Loaded on NaTaO₃:Sr Photocatalysts

CO₂ reduction as an artificial photosynthetic system is a promising technology to produce green energies and chemicals because it uses light energy to convert H₂O and CO₂ into valuable products such as CO, HCOOH, CH₃OH, CH₄, and preferably higher hydrocarbons. In photocatalytic reduction, water should be used as hydrogen and electron sources for CO₂ reduction. Moreover, CH₄ formation is an attractive and challenging topic because of the eight-electron-reducing product of CO₂. Herein, we report the development of a new Rh-Ru cocatalyst decorated on an alkaline earth-doped NaTaO₃ surface for the photocatalytic CO₂ reduction to form CH₄ using water as an electron donor. CH₄ was obtained by a photocatalytic “uphill” reaction of CO₂ reduction using Rh-Ru cocatalyst-loaded NaTaO₃:Sr, water, and CO₂ in an aqueous suspension system. About 10% of a selectivity (electronic efficiency) was obtained for CH₄ formation under ambient conditions accompanied with O₂ evolution of the oxidation product of H₂O.