Reduced TiO2 with tunable oxygen vacancies for catalytic oxidation of formaldehyde at room temperature

Abstract

A series of reduced TiO2 were prepared using NaBH4 and the commercial Degussa P25 as the precursors by tuning the reaction time, and used for catalytic oxidation of HCHO at ambient conditions. Multiple techniques, i.e., UV–Vis, XRD, BET, SEM, TEM, Raman and XPS were used for catalyst characterization. The reduction time was found to remarkably affect the surface oxygen vacancies and surface disorder of the catalysts. Compared with P25, the reduced TiO2 were able to catalytic oxidation of formaldehyde at room temperature under dark condition since the rich surface oxygen vacancies, beneficial for the formation of surface hydroxyl groups and surface active chemisorbed oxygen (e.g., O2– and O−) which are useful to adsorb and/or oxidize formaldehyde. TiO2 reduced for 30 min was found most active for formaldehyde removal owing to the optimal amount of surface oxygen vacancies. A possible mechanism for formaldehyde degradation and catalyst deactivation were also proposed by using in situ DRIFTS study. Moreover, the reduced TiO2 supported low-loading Pd simultaneously exhibited superior activity toward CO2 and stability for formaldehyde oxidation in comparison with P25 supported Pd. This study sheds new light on the TiO2-based catalysts directly for formaldehyde degradation.