Enhanced electrochemical oxidation of phenol using a hydrophobic TiO2-NTs/SnO2-Sb-PTFE electrode prepared by pulse electrodeposition

Abstract

In this study, novel Sb-doped SnO₂ electrodes with a polyetrafluoroethylene (PTFE) composite were fabricated by pulse electrodeposition. In this process, vertically aligned TiO₂ nanotubes (TiO₂-NTs) formed by anodization of Ti plates served as the substrate for SnO₂ eletrodeposition. Comparing with the conventional SnO₂-Sb electrodes, TiO₂-NTs/SnO₂-Sb-PTFE electrodes have higher oxygen evolution potential, improved surface hydrophobicity, superior hydroxyl radical (HO˙) generation and enhanced electrocatalytic activity by incorporation of PTFE nanoparticles. Field emission scanning electron microscopy (FESEM) shows that the surfaces of the PTFE composite electrodes exhibit a microspherical structure. Energy-dispersive X-ray spectroscopy (EDS) confirms the uniform distribution of Sn, Sb, F and C on TiO₂-NTs/SnO₂-Sb-PTFE surfaces. More importantly, the electrodes exhibit a distinctive improvement of oxygen evolution potential (OEP) from 2.0 to 2.4 V (vs. Ag/AgCl). The electrochemical impedance of TiO₂-NTs/SnO₂-Sb-PTFE also decreases significantly compared with Ti/SnO₂-Sb(conventional). The electrocatalytic performance of TiO₂-NTs/SnO₂-Sb-PTFE compared with Ti/SnO₂-Sb(conventional) and TiO₂-NTs/SnO₂-Sb were investigated using phenol as the model pollutant. The effects of initial solution pH and types of supporting electrolyte were investigated. The removal efficiency of total organic carbon (TOC), specific UV absorbance at 254 nm (SUVA₂₅₄), mineralization current efficiency (MCE) and energy consumption (E_c) with respect to different PTFE loadings on the electrodes were investigated. The anodic leaching of Sn ions was also studied under different conditions.