Photocatalytic degradation of phenol by char/N-TiO2 and char/N-F-TiO2 composite photocatalysts

Pyrolytic char/N-TiO2 (CTN), pyrolytic char/N-F-TiO2 (CTNF) and activated pyrolytic char-TiO2 (ACT) composite catalysts have been successfully prepared by a sol-gel method. TiO2 anatase was the major phase formed in all doped catalysts with a small fraction of brookite phase observed for CTN and ACT. UV-vis diffuse reflectance spectroscopy showed a decrease of band gap energy for all doped CTN and CTNF catalysts. The photocatalytic activity of the studied photocatalysts was systematically investigated under visible light and simulated solar light irradiation, by monitoring the degradation of phenol in aqueous suspensions. CTN and CTNF catalysts showed a better photocatalytic efficiency compared to ACT catalysts. The CTNF composite with a ratio of [pyrolytic char]/[N-F-TiO2] = 0.2/2 was found to be the most effective catalyst for phenol removal. According to our results, the pyrolytic char presented favorable adsorption characteristics for phenol and acts as an electron-acceptor from doped-TiO2 particles resulting in decreased e(-) h(+) pair recombination and subsequently in enhanced production of HO center dot. Moreover, it was revealed that N-F modification promotes the e- separation in TiO2 concomitantly with an enhancement in the visible spectral absorbance. (C) 2016 Elsevier B.V. All rights reserved.