Formation of oxygenated polycyclic aromatic hydrocarbons by photoelectrocatalysis using TiO2 nanotubes

Abstract

The transformation intermediates of the polycyclic aromatic hydrocarbons (PAHs), including the oxygenated PAHs in photoelectrocatalytic (PEC) processes has seldom been reported. In this study, anthracene (Ant), a typical PAH, was selected as the target compound. The main transformation intermediates including anthranone (AT) and anthraquinone (AQ) were analyzed in a PEC process using TiO₂ nanotubes (TNTs) as a photoanode with simulated solar light irradiation and a bias potential. AT and AQ were demonstrated to be formed from Ant in the PEC process. However, the elimination of AT and AQ was hardly observed when Ant was mostly eliminated. The PEC process efficiently enhanced the elimination of Ant, as well as the total molar concentration of Ant, AT and AQ, compared with the photocatalysis and electrochemical oxidation process. The PEC process achieved a best elimination efficiency at 1.0 V bias and pH 2.0. The elimination efficiency decreased with the increase of the Ant initial concentration. The effect of humic acid was explored. It was concluded that the ˙O₂⁻ radical was more effective than ˙OH for the transformation of Ant to AT and AQ. Furthermore, compared with the UV light photocatalysis (PC), the PEC process could save much energy in the aspect of Ant elimination.