Highly active Pt/NaxTiO2 catalyst for low temperature formaldehyde decomposition

Abstract

A series of titania nanowires containing different Na content (NaxTiO2) were prepared from sodium titanate by varying the pH value of ion-exchange. They were used to load the Pt nanoparticles for low temperature formaldehyde catalytic oxidation. As prepared samples were systematically characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), temperature programmed reduction/desorption/oxidation (TPR/TPD/TPO) and so on. The results showed that NaxTiO2 were consisted of anatase and sodium titanate. As pH value increased, the surface area and anatase content of catalyst decreased. Pt particles on NaxTiO2 were more easily oxidized and had smaller size but less exposed atoms compared with those on pure TiO2. The HCHO catalytic oxidation result exhibited that Pt/NaxTiO2 catalysts possessed excellent HCHO catalytic oxidation at ambient temperature that were 8.9–52.8 times the activities as that of Pt/TiO2. Kinetic studies manifested the easy activation of HCHO reaction over Pt/NaxTiO2 catalysts. Structure-performance analysis showed that the enhanced performance of Pt/NaxTiO2 catalysts was mainly attributed to two factors: increase in HCHO adsorption amount and change in HCHO decomposition pathway. According to HCHO-DRIFTS, linearly adsorbed CO generated from formate can react with hydroxyls to be carbonate/bicarbonate over Pt/NaxTiO2 catalysts. Simultaneously, the formate in Pt/NaxTiO2 catalyst with high Na content was also decomposed into a weak adsorbed CO. Both reaction pathways avoided the strong adsorption of CO on Pt/NaxTiO2 catalysts, which can facilitate the HCHO decomposition.