Polymerizable Complex Synthesis of RuO₂/BaTi₄O₉ Photocatalysts at Reduced Temperatures:  Factors Affecting the Photocatalytic Activity for Decomposition of Water

Abstract

Phase-pure BaTi 4 O 9 powders were prepared at temperatures higher than 700 °C by the Pechini-type polymerizable complex (PC) technique, based upon polyesterification between citric acid and ethylene glycol. BaTi 4 O 9 was subsequently converted to nanocomposite materials by modifying its surface with ultrafine particles of RuO 2, and the nanocomposite was used as photocatalyst for the decomposition of water into H 2 and O 2 . The RuO 2 /PC-BaTi 4 O 9 material prepared at 800 °C showed a photocatalytic activity ∼5 times higher than that of a sample prepared by a solid-state reaction at 1100 °C. The activity did not scale simply with the specific surface area of the samples; e.g. the sample having a surface area of 20.4 m 2 /g (prepared at 700 °C ) showed, unexpectedly, a ∼50% reduction in the activity when compared with that of a sample having a surface area of 7.6 m 2 /g (prepared at 800 °C ). The anomalous reduction in the activity was interpreted as a consequence of the increased number of lattice defects acting as inactivation centers. The average emission lifetime estimated from an emission decay curve decreased from 4.0 to 2.5 ns with a decrease in the preparation temperature from 900 to 700 °C, suggesting that the number of lattice defects is increased as the temperature is lowered.