CHEMICAL ENGINEERING TRANSACTIONS VOL. 47, 2016 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Angelo Chianese, Luca Di Palma, Elisabetta Petrucci, Marco Stoller Copyright © 2016, AIDIC Servizi S.r.l., I SBN 978-88-95608-38-9; I SSN 2283-9216 Synthesis of Nanostructured Materials for Photoelectrochemical Oxidation of Organic Compounds Laura Mais* a , Pablo Ampudia a , Simonetta Palmas a , Annalisa Vacca a , Michele Mascia a , Francesca Ferrara b a Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, Italy b Sotacarbo S.p.A., c/o Grande Miniera di Serbariu, 09013 Carbonia, Italy l.mais@dimcm.unica.it The present work relates to the use of titanium dioxide nanotubular array (NT) as photoanode for the photoelectrochemical oxidation of phenol used as model of organic compounds. Moreover, surface modification of NT structures has been carried out by deposition of tungsten oxide in order to enhance the response of the system toward wave lengths in the near visible range. Nanotubular structures were prepared by electrochemical oxidation of Ti foils in a water / organic solution with 0.14 M of NH 4 F at room temperature. Tungsten oxide was electrochemically deposited on NTs structures in a hierarchical structure. The electro- and photoelectro-oxidation of phenol was studied in a typical three-electrode cell equipped with a quartz window. Irradiation of the photoanode was performed by a Xenon lamp (nominal power 300 W). Different electrochemical techniques, such as potential ramps and potential steps were adopted to investigate the performance of the system. SEM analysis was also performed to investigate on the morphology of the photoanode. Spectrophotometric analyses have been used to analyse the variation of the organic compound concentration. 1. Introduction Nowadays, the contamination of natural and drinking water supplies and of the aquatic environment has become a serious environmental problem worldwide. Phenolic compounds are major pollutants of the aquatic environment due to their widespread use in agricultural, petrochemical, textile, paint, plastic, and pesticidal chemical industries. They are well known to be biorecalcitrant and to have acute toxicity with carcinogenic and mutagenic characters (Lathasree et al., 2004). Titanium dioxide (TiO 2 ) has been widely studied as a photocatalyst (PC) for environmental applications, such as purification of waters and wastewaters. Actually, its favourable characteristics, such as remarkable charge transport properties and superior oxidation ability, long-term chemical stability, non-toxicity, inertness and low price, make it competitive with respect to other semiconductors (Qin et al., 2012). The TiO 2 features determine to a great extent the efficiency and the performance of the degradation process. Under illumination, the photogenerated holes (free in the valence band or trapped at surface states) are responsible for oxidizing the organic substrates. However, the low utilization efficiency of visible light and the high recombination rate of photoinduced electron–hole pairs, hold back its application in water treatment. Photoelectrocatalysis (PEC) promotes the separation of electron–hole pairs by driving the electron transfer to an external circuit: thanks to the applied potential bias a significant enhance of the PC efficiency, by suppressing the recombination of photogenerated electrons and holes, can be achieved (Zhang et al., 2012). In PEC processes, the degradation rate of organic pollutants depends, to some extent, on the activity of the photoanode; therefore, improving its activity has become a primary research focus. One of the most studied approaches to increase the activity of TiO2 is compositional doping with anions or transition metals (Shankar et al., 2009). Another approach is coupling TiO 2 with another metal oxide with narrower bandgap, such as WO 3 (Eg=2.6 eV); this coupling approach is expected to provide a better charge DOI: 10.3303/CET1647027 Please cite this article as: Mais L., Ampudia P., Palmas S., Vacca A., Mascia M., Ferrara F., 2016, Synthesis of nanostructured materials for photoelectrochemical oxidation of organic compounds, Chemical Engineering Transactions, 47, 157-162 DOI: 10.3303/CET1647027 157