Electrochemical Preparation And Properties Of Aluminum - Based Lead Dioxide Composite Inert Anode Materials

The Pb-(0.75～1%)Ag alloy as anode material are being widely used in zinc electrowinning industry at present. However, it has some shortcomings, such as high oxygen evolution overpotential, poor electroconductivity, low mechanical strength, and it can reduce the quality of cathode zinc products caused by anodic dissolution. The lead dioxide (PbO2) has got broad attention, because of its strong acide and alkali resistance, good electroconductivity, etc.The Al/Pb/α(β)-PbO2-WC(Co3O4) composite inert anode materials were prepared by constant current electrodeposition of α(β)-PbO2depositions doped with WC and CO3O4particles from alkaline and acidic solutions respectively. Of which, the Al/Pb was used as substrate in this paper. The effects of the conditions such as the compositions and temperature of plating solutions, the addition amount of particles and the stirring speed on the electrodeposition of α(β)-PbO2were studied. And the influences of the ultrasonic time and surfactant on the dispersity of WC and Co3O4in α(β)-PbO2plating solutions were investigated. The physical (such as surface microhardness, electrical resistivity, etc) and electrochemical (such as oxygen evolution electrocatalysis activity, corrosion resistance and AC impedance characteristics in zinc electrowinning simulated system) properties of the composite inert anode materials were tested. The main conclusions obtained through the study are as follows:The oxygen evolution electrocatalysis activity of Al/Pb/α(β)-PbO2composite inert anode materials was not as good as Pb-1%Ag alloy, however, their corrosion resistance was better than it. The α-PbO2electrodeposited in the alkaline plating bath possessed the rhombic structure with well developed spherical unit cell. The β-PbO2electrodeposited from the acidic plating bath presented the octahedral and rutile structure.The electroconductivity and oxygen evolution electrocatalysis activity of the Al/Pb/α-PbO2composite inert anode material were enhanced by doping WC and Co3O4into α-PbO2. Of which, the surface microhardness of Al/Pb/α-PbO2-WC composite inert anode material was the highest (471.1HV), and its resistivity was the lowest (1.98Ω·cm). In addition, its corrosion resistance in zinc electrowinning simulated system was the best. The oxygen evolution overpotential of Al/Pb/α-PbO2-Co3O4composite inert anode material in zinc electrowinning simulated system was the lowest (0.793V) when current density was 500m A/cm2.The surface microhardness and electroconductivity of the β-PbO2composite inert anode material, and its oxygen evolution electrocatalysis activity as well as corrosion resistance in zinc electrowinning simulated system could be improved by doping WC and Co3O4into β-PbO2. Of which, the surface microhardness of Al/Pb/α-PbO2-WC/β-PbO2-WC composite inert anode material was the highest (917.7HV), and its resistivity was the lowest (0.653Ω·cm). But its oxygen evolution electrocatalysis activity was poor. The oxygen evolution overpotential of Al/Pb/α-PbO2-WC/β-PbO2-WC-Co3O4composite inert anode material in zinc electrowinning simulated system was the lowest (0.628V) when current density was500mA/cm2. Its Tafel constant value, i.e., a and b, were the minimum (1.157V and0.534V respectively). In addition, its surface microhardness was higher (722.1HV), and resistivity was lower (0.697Ω·cm).