Effect of Current Densities on the Microstructure and Electrochemical Behavior of the Porous β-PbO₂ Electrode

Abstract

In order to obtain a titanium-based PbO2 electrode with high electrocatalytic activity and good stability, A porous β-PbO2 electrode is prepared by electrodepositing on titanium substrate Sn-Sb-RuOx coating. The surface morphology and phase analysis of the porous β-PbO2 electrode prepared at different current density were investigated by SEM and XRD. Results showed that the current density changes the surface morphology and active surface area of the porous β-PbO2 electrode. When the current density is 2 A/dm2, the surface of the porous β-PbO2 prepared by electrodeposition has a uniform porous morphology with a pore diameter of 50-200 µm with main crystal phase of β-PbO2. Influence of current density on the electrochemical activity of the electrode was analyzed using anodic polarization curve, electrochemical impedance spectroscopy and galvanostatic polarization. Results revealed that with the increase of current density, the oxygen evolution potential of the porous β-PbO2 electrode decreases first and then increases while the exchange current density first increases and then decreases. When the current density is 2 A/dm2, the oxygen evolution potential is 2.0075 V(at 0.05 A/cm2) and the maximum exchange current density is 1.77×10-4 A/cm2. According to the electrochemical impedance spectroscopy, when the current density is 2 A/dm2, Qf and Qdl are the largest, Rf and Rct are the smallest, and the RF first increases and then decreases with the current density increases. When the current density is 2 A/dm2, the maximum RF value is 655.7. The results with galvanostatic polarization at current density of 0.05 A/cm2 showed that the electrode has a minimum electrode voltage of 2.05 V at a current density of 2 A/dm2. Accelerated life experiments were carried out in 2 g/L Cl- and 150 g/L H2SO4 bath at 25 °C, and the porous β-PbO2 electrode obtained under the current density of 2 A/dm2 has the longest life, and the electrode life is 68 h, which is 2.5 times of the PbO2 electrode obtained under the current density of 4 A/dm2.