Laser synthesized TiO2-based nanoparticles and their efficiency in the photocatalytic degradation of linear carboxylic acids

Sarah Bouhadoun,Chantal Guillard,Sébastien Sorgues,Alexandre Hérissan,Christophe Colbeau-Justin,Frederic Dapozze,Aurélie Habert,Vincent Maurel,Nathalie Herlin-Boime

doi:10.1080/14686996.2017.1379858

Abstract

Titanium dioxide nanoparticles were synthesized by laser pyrolysis, their surface and electronic properties were modified by gold and/or nitrogen. These materials were characterized by different techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Time resolved conductivity (TRMC) was used to study the charge separation of electron/hole pairs. Altogether (XPS, EPR, TRMC), the physicochemical characterizations are well correlated with chemical photoactivity of the different samples. Their photocatalytic activity was evaluated for the degradation of linear carboxylic acids (C2-C3) under UV and visible illumination. The decomposition rate of acids was measured, it shows that the modification with gold increases the photoactivity while the presence of nitrogen slows down the process. Such observations are in good agreement with evolution of TRMC signals. A degradation pathway has been determined by identification of intermediate products by chromatography and EPR, results show different intermediate species. In particular EPR confirms the presence of NO2− paramagnetic centers and shows two novel N centered paramagnetic centers. A decrease of the degradation rate is observed with increase of carboxylic acid chain length.

Highlights

Many studies deal with the fabrication and characterization of the photocatalytic activity of various materials exhibiting efficiency both in the visible and UV range [1,2,3]
The samples were synthesized by laser pyrolysis in similar conditions, except the choice of the reactive mixture injected in the laser beam
The surface modification of titania by gold and/or nitrogen was successfully performed by using laser pyrolysis method

Summary

Introduction

Many studies deal with the fabrication and characterization of the photocatalytic activity of various materials exhibiting efficiency both in the visible and UV range [1,2,3]. Different ways to enhance the visible photoactivity are doping by hetero-elements (N, S, F,...) or introducing metallic structures (Au, Ag...) with an absorption in the visible range and/or able to improve the charge separation [8,9,10,11,12,13,14]. In this context, we have previously demonstrated that the laser pyrolysis is an efficient method for the one step synthesis of TiO2-based nanomaterials

Methods

Results

Conclusion