Ionic Liquids Assisted Electrodeposition and Electrocatalytic Activity of PbO2 electrodes

PbO2 coatings were electrodeposited on titanium substrates from solutions containing Pb(NO3)(2) in the presence of an ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim]BF4) by anodic oxidation technique. Influences of [Emim]BF4 concentration and bath temperature on crystalline structure and electrocatalytic activity of resulting PbO2 deposits were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical oxidation of phenol simulated wastewater, respectively. A highly textured crystalline structure of beta-PbO2 with (110) plane being preferred orientation peak was obtained in the presence of [Emim]BF4. An increase in [Emim]BF4 concentration resulted in a higher degree of crystallinity and improved electrocatalytic activity of resulting deposits. Moreover, the crystalline structure of PbO2 coatings was also greatly affected by bath temperature. The ratio of alpha-PbO2/beta-PbO2 phases decreased with the increase in bath temperature. The preferential crystallographic orientation for beta-PbO2 in the (110) direction became more pronounced at higher temperatures. PbO2 coatings with the optimum electrocatalytic activity were obtained in the presence of 50 mg.L-1 [Emim]BF4 at 50 degrees C. The activity of PbO2 electrodes was found to be strongly dependent on their phase composition, degree of crystallinity and crystallite orientation.