Synthesis of RuO₂-loaded BaTi_nO_{2n + 1} (n = 1, 2 and 5) using a polymerizable complex method and its photocatalytic activity for the decomposition of water

A polymerizable complex (PC) technique was utilized to prepare fine powders of high purity BaTi_nO_{2n + 1} with n = 1, 2 and 5 at lower temperatures than those used for the ordinary solid-state reaction procedure. The formation of pure BaTi_nO_{2n + 1} occurred when precursors obtained from PC-derived gel materials were heat-treated at 800-900°C in static air for 2 h. BaTi_nO_{2n + 1} powders were subsequently converted to RuO₂-loaded materials, and their photocatalytic activities for the decomposition of water were examined. While the RuO₂-BaTi₂O₅ (n = 2) and RuO₂-BaTi₅O₁₁ (n = 5) materials exhibited photocatalytic activity for water decomposition into H₂ and O₂ in approximately stoichiometric amounts (H₂:O₂ = 2:1) under UV light irradiation with specific hydrogen gas evolution rates of 125 and 52 μmol h^-1 g^-1, respectively, the RuO₂-BaTiO₃(n = 1) exhibited a very low activity of less than 1 μmol h^-1 g^-1. The lack of a significant occurrence of photocatalysis in BaTiO₃ was explained in terms of its crystal structure possessing only a very small polyhedral distortion.