Highly Active NaTaO3 -Based Photocatalysts for CO2 Reduction to Form CO Using Water as the Electron Donor

Abstract

Doped NaTaO₃ (NaTaO₃ :A, where A=Mg, Ca, Sr, Ba, or La) has arisen as a highly active photocatalyst for CO₂ reduction to simultaneously form CO, H₂ , and O₂ using water as the electron donor when used with an Ag cocatalyst, under UV irradiation, and with 1 atm (0.1 MPa) of CO₂ . The ratio of the number of reacted electrons/holes was almost unity, indicating that water was consumed as the electron donor. A liquid-phase reduction method for loading of the Ag cocatalyst was superior to photodeposition and impregnation methods. The Ag cocatalyst-loaded NaTaO₃ :Ba was the most active photocatalyst in water with no required additives. The addition of bases, such as hydrogencarbonate, was effective to enhance the CO formation for Mg-, Ca-, Sr-, Ba-, and La-doped NaTaO₃ photocatalysts with an Ag cocatalyst. Ca- and Sr-doped NaTaO₃ photocatalysts showed especially high activity along with the Ba-doped photocatalyst in the aqueous NaHCO₃ solution. The selectivity for the CO formation [CO/(CO+H₂ )] on Ca-, Sr-, and Ba-doped NaTaO₃ photocatalysts with Ag cocatalyst reached around 90 %.

Keywords: alkali earth metals; carbon dioxide fixation; electron donor; energy conversion; photocatalysis.