工程科学学报 (Oct 2019)
Preparation and properties of Al-rod-Pb-0.2%Ag composite anode by surface ceramization
Abstract
To obtain a low-cost anode with low oxygen evolution potential and high catalytic activity for zinc electrowinning, Pb-0.2%Ag alloy was coated on an aluminum matrix surface by extrusion cladding technology, and a film layer with high catalytic performance was formed on the surface of the Pb-0.2%Ag alloy and Al-rod-Pb-0.2%Ag anode by anodization in a fluorine-containing sulfuric acid solution. The thickness and hardness of the film were studied using a microscopic image analyzer and digital microhardness tester, and the ultimate tensile strengths of the two anodes were compared using an electronic tensile tester. The phase, morphology, and electrochemical performance of the Al-rod-Pb-0.2%Ag and Pb-0.2%Ag anode surface film were investigated using X-ray diffractometry, scanning electron microscopy, cyclic voltammetry, anodic polarization, and electrochemical impedance spectroscopy. The results show that the Al-rod-Pb-0.2%Ag anode surface forms a dense and thick oxide film layer more easily than the Pb-0.2%Ag anode and the hardness of the film layer is increased by 41.64%; moreover, the main phase is β-PbO2, and the oxide film layer exhibits good electrocatalytic activity. The ultimate tensile strength of the new anode was 1.3 times that of the traditional anode, which greatly improves the mechanical properties of the anode material. Analytical data of anodic polarization curves reveal that the Al-rod-Pb-0.2%Ag/PbO2 anode shows low oxygen evolution potential (1.35 V vs MSE, 500 A·m-2) and high exchange current density (7.079×10-5 A·m-2) in zinc electrowinning system. Analytical data of cyclic voltammetry and EIS curves indicate that the Al-rod-Pb-0.2%Ag/PbO2 anode has higher electrocatalytic activity, larger surface roughness, and smaller charge transfer resistance. In the zinc electrowinning experiment, the average cell voltage of the fence-like Al-rod-Pb-0.2%Ag/PbO2 anode was 75 mV less than that of the traditional Pb-0.2% Ag anode, and the production of anode slime was greatly reduced.
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