Effect of cerium content and post-thermal treatment on doped anisotropic TiO2 nanomaterials and kinetic study of the photodegradation of formic acid

Abstract

In this work, the design of cerium doped TiO2 nanomaterials with tuned structural and textural properties is reported. The influence of the cerium content of doped TiO2 solids (x=1 to 5wt%) on the photocatalytic degradation of formic acid using UV-A light was evaluated.The best photocatalytic activity was reached for 1wt% of cerium.The effect of post-thermal treatments was also herein highlighted by varying the calcination temperature between 400°C and 700°C for simultaneously doped- and cerium-free TiO2 samples. Characterization was performed by means of nitrogen adsorption–desorption isotherms at 77K, X-ray diffraction, Raman spectroscopy, Photoluminescence (PL) spectroscopy, and diffuse reflectance UV–vis spectroscopy. The presence of Ce limits the growth of TiO2 crystallite sizes during the post-thermal treatment and favors stabilization of the TiO2 anatase phase. The presence of cerium also increases the number of surface defects and transforms them to non-radiative centers able to capture the photogenerated electrons as observed by PL spectroscopy. This would leave photogenerated holes available improving consequentlythe photocatalytic activity for the oxidation of formic acid. Finally, a possible pathway mechanism is proposed to confirm the obtained results.