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, ρav, was 1.8 nm for BTO and 5.1 nm for KTO) than did the chloride (ρav 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.