Preparation and Characterization of [Emim]BF4 Modified Lead Dioxide Electrodes

Abstract:

Modified PbO₂ electrodes were prepared by electrodeposition in the presence of ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim]BF₄). The electro-catalytic performance of prepared electrodes for the electrochemical degradation of phenol in aqueous solution was investigated. The COD removal of phenol simulated wastewater followed pseudo-first-order rate kinetics. The first-order rate constant with [Emim]BF₄-modified PbO₂ electrodes was 0.00739 min_-1, versus 0.00383 min_-1 obtained with non-modified PbO₂ electrodes. The microstructure of the electrodes was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The electrochemical properties were investigated by Mott-Schottky, steady-state polarization and linear sweep voltammetry techniques. The surface characterization results illustrated that PbO₂ coatings with compact and regular morphology, a higher degree of crystallinity and higher content of oxygen in crystal lattice were anodically grown on Ti substrate from electrolyte containing [Emim]BF₄. Steady-state polarization tests showed that oxygen evolution overpotential on modified electrodes was significantly higher than that on non-modified electrodes. Mott-Schottky tests revealed a markedly lower content of oxygen vacancy in modified PbO₂ samples as compared with the non-modified ones. It was suggested that the enhanced electro-catalytic activity of the [Emim]BF₄-modified PbO₂ electrode towards phenol degradation arose largely from the lower content of oxygen vacancy, which decreased the probability of oxygen transfer from more effective ?OH into less desirable O_lat at the electrode surface.