Fine crystals of potassium hexatitanate prepared by a sol-gel method for photocatalytic reduction of carbon dioxide with water

Potassium hexatitanate photocatalysts with Ag cocatalyst (Ag/K2Ti6O13, Ag/KTO) can selectively exhibit the photocatalytic CO2 reduction to CO with water, and the preparation method and its conditions are known to much influence the photocatalytic activity. In the present study, to investigate the relationship between the structure and photocatalytic activities of crystal photocatalyst, the fine rod-like KTO samples with various crystal size are prepared by a sol-gel method. The required conditions were investigated to obtain pure KTO crystals without TiO2 impurity phase. The use of some additives for the preparation provided variously sized fine KTO crystals. By using obtained sub-micrometer sized pure KTO crystal samples, it is revealed that the KTO crystals consisting of larger crystals tend to give higher activity. This proposed that the crystals of larger maximum crosssectional area, which can receive many photons, exhibit higher photocatalytic activity for the CO2 reduction with water in the present conditions.