Alexandre Hérissan

Visible light-induced photocatalytic activity of modified titanium(IV) oxide with zero-valent bismuth clusters

The important challenge in photocatalysis is to find efficient and stable photocatalysts under visible light. Small Bi zero-valent clusters were synthesized on TiO2-P25 by radiolysis. Photocatalytic tests were conducted under UV, visible and solar light with rhodamine B and phenol as model pollutants. Surface modification of TiO2 with zero-valent Bi nanoclusters induces high photocatalytic activity under visible light. Very small amounts of Bi (0.5 wt%) can activate titania for photocatalytic applications under visible light. Time resolved microwave conductivity measurements indicate that under visible irradiation Bi nanoclusters inject electrons into the conduction band of TiO2. These photocatalysts are very stable with cycling.

Laser synthesized TiO

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.