Alkali hexatitanate photocatalysts with various morphologies for selective reduction of carbon dioxide with water

Abstract

Various alkali–metal hexatitanate photocatalysts were examined for photocatalytic reduction of carbon dioxide with water. Four types of alkali–metal hexatitanate samples (A₂Ti₆O₁₃, A = Na, K, Rb, and Cs) were correctly prepared by either a flux method or a solid-state reaction method. Among them, the potassium hexatitanate (K₂Ti₆O₁₃: KTO) photocatalyst exhibited the highest activity and selectivity to CO formation. Further development of the KTO photocatalyst was examined by changing preparation conditions such as different fluxes, the ratio of flux and substrate, and the calcination temperature, which provided various morphologies, structures, and photocatalytic activities. Among the examined samples, an Ag/KTO photocatalyst consisting of rod-like KTO crystals with a suitable length and width, prepared with a KCl flux at 1273 K for 10 hours and loaded with an Ag cocatalyst, gave the highest activity for CO evolution (4.3 μmol h⁻¹) and the highest selectivity toward CO (96%).