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

Mg, Ca, Sr, Ba and La-doped NaTaO3 has arisen as highly active photocatalysts for CO2 reduction to form CO using water as an electron donor accompanied by O2 evolution under UV irradiation and bubbling of 1 atmosphere of CO2 when an Ag cocatalyst was loaded on those photocatalysts. CO, H2 and O2 simultaneously formed. The ratio of the number of reacted electrons to that of holes was almost unity. This result indicated that water was consumed as an electron donor. A liquid-phase reduction method for loading of the Ag cocatalyst was superior to photodeposition and impregnation methods. Ag cocatalyst-loaded NaTaO3:Ba was the most active photocatalyst in water with no additives. 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 especially showed high activity as well as 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%.