TiO2–Hydroxyapatite Composite as a New Support of Highly Active and Sintering-Resistant Gold Nanocatalysts for Catalytic Oxidation of CO and Photocatalytic Degradation of Methylene Blue

Abstract

Supported gold catalysts have attracted intensive interest due to their unique catalytic properties. The easy sintering of gold particles, however, is still the major obstacle to the practical application of gold catalysts. Herein, a highly active and sintering-resistant TiO2–hydroxyapatite (HAP, Ca10(PO4)6(OH)2) composite supported gold catalyst was prepared by a deposition–precipitation method. TEM results manifested TiO2–HAP had smaller gold nanoparticles than TiO2 and HAP. Patterns of TG–DTG revealed that the presence of HAP inhibited the phase transformation from anatase to rutile. Based on UV–Vis and BET studies, HAP prevented the formation of large TiO2 agglomerates, leading to higher dispersion of TiO2 nanoparticles in TiO2–HAP composites. Au/TiO2–HAP had the higher activity and sintering-resistance compared with Au/TiO2 and Au/HAP for CO oxidation. TiO2–HAP and Au/TiO2–HAP exhibited the best photocatalytic activity among supports and gold nanocatalysts, respectively. Gold nanoparticles could further improve the photocatalytic performance. It was likely that the synergistic interaction among gold nanoparticles, TiO2 and HAP was responsible for the high activity and sintering-resistance of Au/TiO2–HAP.