Influence of rare earths doping on the structure and electro-catalytic performance of Ti/Sb–SnO2 electrodes

Rare earth Ce, Eu, Gd and Dy doped Ti/Sb–SnO2 electrodes were prepared by thermal decomposition and the performance of electrodes for the electro-catalytic decomposition of a model pollutant (phenol) was investigated. Phenol degradation and TOC removal followed pseudo-first-order kinetics in the experimental range, with the maximum rate achieved using Gd-doped electrode and the minimum rate obtained by Ce-doped electrode. Electrodes were characterized by cyclic voltammetry, X-ray diffraction, electron dispersive spectrometry, and X-ray photoelectron spectroscopy. It was suggested that the enhanced performance of the Gd-doped Ti/Sb–SnO2 electrode arose from the increased adsorption capacity of hydroxyl radicals on the electrode surface and the lower mobility of oxygen atoms in SnO2 lattice. The redox couple of Ce4+/Ce3+ on Ce-doped Ti/Sb–SnO2 electrode surface functioned as mediators in the electrochemical oxidation process, allowing oxygen transfer in the SnO2 lattice, and lowered the electro-catalytic ability of the electrode on phenol mineralization.