Preparation and properties of Al-rod-Pb-0.2%Ag composite anode by surface ceramization
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摘要: 為獲得一種鋅電積用低成本、低析氧電位和高催化活性的陽極,在鋁棒表面通過擠壓復合技術包覆Pb-0.2% Ag合金得到Al棒Pb-0.2% Ag陽極.在含氟的硫酸溶液中,通過陽極氧化在Pb-0.2% Ag合金和Al棒Pb-0.2% Ag合金陽極表面形成具有高催化性能的膜層,采用顯微圖像分析儀和數顯顯微硬度計表征了膜層的厚度及硬度,并通過電子拉伸試驗對比了兩種陽極的極限抗拉強度.采用X射線衍射、掃描電子顯微鏡、循環伏安法、陽極極化和交流阻抗法等技術手段研究了Al棒Pb-0.2% Ag與Pb-0.2% Ag陽極表面氧化膜層的物相、形貌以及電化學性能.結果表明:Al棒Pb-0.2% Ag陽極相比Pb-0.2% Ag陽極表面易生成致密較厚的氧化膜層,且膜層硬度提升了41.64%,其氧化膜層主要物相均為電催化活性良好的β-PbO2.新型陽極的極限抗拉強度是傳統陽極的1.3倍,大大改善了陽極材料的機械性能.陽極極化曲線數據顯示Al棒Pb-0.2% Ag/PbO2陽極在電積鋅體系中具有較低的析氧電位(1.35 V vs MSE,500 A·m-2)和較高的交換電流密度(7.079×10-5 A·m-2).循環伏安曲線和交流阻抗數據顯示Al棒Pb-0.2% Ag/PbO2陽極具有較高的電催化活性、較大的表面粗糙度和較小的電荷傳質電阻.在電積鋅實驗中,柵欄型Al棒Pb-0.2% Ag/PbO2陽極相比傳統Pb-0.2% Ag陽極平均槽電壓下降了75 mV,而且大大減少了陽極泥的產生.
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關鍵詞:
- Al棒Pb-0.2%Ag /
- 表面陶瓷氧化 /
- 鋅電積 /
- 機械性能 /
- 電催化活性
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. -
圖 5 不同陽極材料的表面膜層截面金相及力學性能.(a) Al棒Pb-0.2%Ag; (b) Pb-0.2%Ag; (c) 極限抗拉強度; (d) 膜層厚度與維氏硬度
Figure 5. Metallographic and mechanical properties of the surface layer of different anode materials: (a) Al-rod-Pb-0.2%Ag; (b) Pb-0.2%Ag; (c) ultimate tensile strength; (d) Vickers hardness and thickness of surface layer
圖 8 不同陽極材料在50 g·L-1 Zn2+, 150 g·L-1 H2SO4溶液中的交流阻抗圖. (a) 阻抗圖譜; (b) Bode圖; (c) 擬合電路圖
Figure 8. EIS spectra of the different anode materials in 50 g·L-1 Zn2+, 150 g·L-1 H2SO4 solution: (a) Nyquist diagrams; (b) Bode plots; (c) electrical equivalent circuit used to simulate impedance data for OER on composite electrode material
表 1 不同陽極材料的析氧反應動力學參數
Table 1. Kinetic parameters of oxygen evolution for the different anode materials
陽極試樣 η/V a1 b1 a2 b2 J0/(A·m-2) 500 A·m-2 1000 A·m-2 Pb-0.2%Ag 0.894 0.951 1.142 0.191 1.266 0.442 1.049×10-6 Pb-0.2%Ag/PbO2 0.794 0.861 1.083 0.222 1.182 0.438 1.323×10-5 Al棒Pb-0.2%Ag 0.874 0.935 1.139 0.204 1.247 0.428 2.610×10-6 Al棒Pb-0.2%Ag/PbO2 0.741 0.819 1.079 0.260 1.171 0.454 7.079×10-5 表 2 不同陽極材料交流阻抗譜的等效電路參數
Table 2. Equivalent circuit parameters of the EIS spectra of the different anode materials
陽極試樣 Rs/(Ω·cm2) Rt/(Ω·cm2) Qdl/(Ω-1·cm-2·sn) n Cdl/(μF·cm-2) RF Pb-0.2%Ag 0.122 9.532 0.001 0.852 198 9.9 Pb-0.2%Ag/PbO2 0.127 3.176 0.020 0.980 17712 885.6 Al棒Pb-0.2%Ag 0.114 6.423 0.007 0.793 1067 53.4 Al棒Pb-0.2%Ag/PbO2 0.088 2.84 0.044 0.898 23308 1165.4 表 3 電積鋅實驗條件
Table 3. Experimental conditions for zinc electrodeposition
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