Study On Preparation And Photoelectrocatalytic Performance Of PbO₂-TiO₂ Nanocomposite Electrodes

In this paper, PbO₂-TiO₂ nanocomposite electrodes had been prepared by the direct current electrodeposition method in the lead nitrate solution containing TiO₂ nanoparticles. Firstly, the best conditions of direct current deposition preparation had been achieved by investigating TiO₂ nanoparticles content in the electrodes: lead nitrate solution containing 8 g·L-1 TiO₂ nanoparticles with electroplating current density at 30 mA·cm-2, stirring speed at 120 rpm, solution temperature at 30℃. A series of conclusions were proved by the characterization of SEM and XRD, the surface of composite electrodes are more compact and finer than PbO₂ electrode.The service life of PbO₂-TiO₂ nanocomposite electrodes reached 149 h, which was four times longer than that of PbO₂ electrodes. The tests of photoelectrochemical properties of PbO₂-TiO₂ nanocomposite electrodes show that, it has more electrochemical active surface area（EASA） compared with the PbO₂ electrode, and could produce obvious photocurrent under UV irradiation which was in favour of electrocatalytic reaction.Then get the best conditions of preparation by pulse electrodeposition according to examining the influence of weight gain rate on the coating and the the content of TiO₂ nanoparticles in the electrodes: lead nitrate solution containing 8 g·L-1 TiO₂ nanoparticles with peak current density at 50 mA·cm-2, pulse frequency at 10 Hz and pulse duty cycle at 20 %. The characterization of SEM and XRD show that, the surface of composite electrodes by pulse electrodeposition method are more compact and finer, the mean size of particles is more smaller than the direct current electrodeposition. The service life of composite electrodes reached 260 h, which is nearly two times longer than that of electrodes by direct current electrodeposition and above seven times longer than that of PbO₂ electrodes.The tests of photoelectrochemistry show that, PbO₂-TiO₂ nanocomposite electrodes has more EASA and possess remarkable photocurrent response under UV irradiation. On the base of the bias potential, the photoelectrocatalysis efficiency had been improved prominently. The cyclic voltammograms tests found that, PbO₂-TiO₂ nanocomposite electrodes had higher oxygen evolution potential than that of PbO₂ electrodes, so it was more in favour of the degradation of organic pollutants. Electrochemical impedance spectroscopy show that, pulse method could make electron transfer reactions happen more smoothly than direct current method, so can enhance the electrocatalytic oxidation rate.The optimum process conditions of the degradation of RhB had been obtained according to use PbO₂-TiO₂ nanocomposite electrodes by pulse electrodeposition method to remove RhB: bias potential at 1.4 V, RhB initial concentration at 30 mg·L-1, electrolyte concentration at 0.05 mol g·L-1 and initial pH value at 3. The RhB and COD remove efficiency reaches 99.87 % and 78.18 % by photoelectrocatalytic degradation after 90 min. Compared with the direct current composite electrodes and PbO₂ electrodes degradation of RhB, PbO₂-TiO₂ nanocomposite electrodes by pulse electrodeposition possess highest decolorization rate, COD remove rate, fastest catalytic rate and highest instantaneous current efficiency. Therefore, it has the best catalytic properties. The degradation process follow the first-order reaction kinetics. The synergistic effect of photoelectrocatalytic degradation of RhB solution has been investigated in this paper. The results show that, the composite electrodes had evident ability of photoelectric synergistic catalytic. Finally, discussed the mechanism of photoelectricatalytic degradation of pollutants, and the existence of HO· is verified by experiment.