Low temperature design of titanium dioxide anatase materials decorated with cyanuric acid for formic acid photodegradation

Abstract

The influence of cyanuric acid (CA) on the structural, textural, electronic, morphological properties and the photocatalytic activity of titanium dioxide materials (TNCA) were herein evaluated. TNCAs samples were prepared through the sol gel method. The novelty of this work that cyanuric acid; the so far most recalcitrant molecule, is used here as reservoir of nitrogen. The synthesis of TNCAs nanomaterials are performed at low temperature in presence of quaternary ammonium as co-catalyst for anatase growth. Samples were characterized by means of nitrogen adsorption-desorption isotherms at 77 K, X-ray diffraction (XRD), Infrared (ATR), Raman, diffuse reflectance ultraviolet-visible, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic activities of TNCAs and their free counterpart nanomaterials were then evaluated in the photocatalytic degradation of formic acid (FA) as model molecule under UV.X-ray and Raman show success of anatase phase formation at low temperature without any post-calcination. IR-ATR analysis confirms CA grafting onto TiO2 identified by formation of vibration band between Ti and triazine. SEM mapping shows that C, O, Ti, and N are homogeneously distributed in the nanomaterial. Nitrogen adsorption-desorption measurements at 77 K show developed textural properties; the heat of N2 adsorption seems to be affected by CA loading. PL and UV-visible spectroscopies show simultaneously (i) electron trapping by the oxygen vacancy identified by Raman spectroscopy by redshift of Eg1 mode and (ii) the hole is confined by nitrogen. Therefore, the excited electron can move from TiO2 VB to the new sublevels initiated by the introduction of nitrogen which results in quenching of the photoluminescence intensity. The photocatalytic activity of the various TNCAs nanomaterials increases versus CA loading. The highest kLH of TNCA2 (5 wt%) could be explained by short migration time conjugated with lower bulk recombination of the photogenerated electron hole. Keywords: Photocatalysis, Cyanuric acid, Nanohybrids, Formic acid, Kinetics