Effects of RuO2 dispersion on photocatalytic activity for water decomposition of BaTi4O9 with a pentagonal prism tunnel and K2Ti4O9 with a zigzag layer structure

Abstract

Effects of RuO₂ dispersion on the photocatalytic activity for water decomposition of BaTi₄O₉ (BTO) with a pentagonal prism tunnel structure and K₂Ti₄O₉ (KTO) with a zigzag layer structure were studied. These titanates were impregnated with either a RuCl₃ aqueous solution or a Ru₃(CO)₁₂ complex in THF and were subjected to oxidation at high temperatures. In comparison with the chloride, the employment of Ru₃(CO)₁₂ complex gave rise to the higher photocatalytic activity of BTO and a significant improvement of photocatalytic performance of KTO. High resolution transmission electron microscopic observation showed that the carbonyl complex led to the formation of uniformly distributed small RuO₂ particles (average particle size, ρ_av, was 1.8 nm for BTO and 5.1 nm for KTO) than did the chloride (ρ_av was 2.7 for BTO and 15 nm for KTO). The tunnel structure of BTO is shown to have the high capability to disperse RuO₂ as small particles, compared to the zigzag layer. The photoexcited charge formation of KTO with UV irradiation was examined by electron paramagentic resonance (EPR) measurements. A correlation between the photocatalytic activity and the ability of surface lattice O⁻ formation is established for these titanates with different structures. The size effects of RuO₂ particles on photocatalysis are discussed.