活性PbO₂颗粒制备及其增强铅基合金的性能研究

【作者】 石凤浜；

【导师】 郭忠诚； 陈步明；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2011， 硕士

【摘要】 在有色金属锌电积过程中,普遍使用的是Pb-Ag(0.7-1.2%)合金阳极,该合金材料具有成型容易,制造简单等优点,但存在一些不足之处,如寿命短、槽电压高、电流效率和机械性能低等。目前新型二氧化铅电极材料具有耐腐蚀性好、导电性强、析氧过电位高、催化性好、成本低等优点,而引起广泛的关注。本论文在氢氧化钠碱性体系中,利用直流电沉积的方法,在不锈钢基体上电沉积α-PbO2-CeO2-Co3O4复合镀层。研究了电沉积工艺参数对复合镀层的影响。确定了最佳工艺条件：电流密度为1.5 A/dm2, Co3O4 30g/L, CeO2 15 g/L,温度40℃、电沉积时间2h。在此条件下,所制备α-PbO2-CeO2-Co3O4复合镀层含5.43% Co3O4和4.64% CeO2,综合性能较好,硫酸锌电解液中电催化活性较高,SEM图片表明添加活性颗粒Co3O4和惰性颗粒CeO2完全可以改变镀层的表面形貌,表面粗糙和晶粒细化,使镀层的比表面积增大和寿命延长。在不锈钢基α-PbO2-CeO2-Co3O4复合镀层上制备β-PbO2-CNT,对掺杂不同浓度的CNT进行电化学分析,得到最佳掺杂CNT的浓度为20g/L。阳极极化曲线表明该浓度下,不锈钢基/β-PbO2-CNT复合镀层的电催化活性较好,动力学参数a和b值均比不添加CNT镀层电极要小。Tafel曲线表明,掺杂CNT也能改善电极的耐腐蚀性能,但是效果不明显。循环伏安得到掺杂CNT没有改变β-PbO2的反应机理,还原峰发生偏移和减小。扫描电镜图片看出,未添加CNT的β-PbO2镀层的晶粒形貌呈正八面体形状,晶粒相对粗大。添加CNT的β-PbO2复合镀层的晶粒表面不统一。有正八面体的β-PbO2颗粒,还有表面分布的CNT,以及受CNT的影响,表面生成的小的八面体β-PbO2晶粒。用α-PbO2-CeO2-Co3O4/β-PbO2-CNT复合镀层制备出PbO2颗粒,并将PbO2颗粒压入Pb-(1%)Ag阳极表面作为一种新型阳极材料。与传统Pb-(1%)Ag阳极相比,该新型复合电极可使电积锌时的槽电压降低,电流效率提高。更多还原

【Abstract】 Pb-Ag (0.7-1.2%) alloy anodes have been commonly used at Non-ferrous metals zinc electrowinning process, which was easy to be manufactured and simply to be formed. However, there were also some shortcomings, such as short lifetime, high cell voltage, low current efficiency and mechanical properties. At present, A great interest was attracted in the improvement of lead dioxide as zinc electrowinning anode material, owing to its good corrosion resistance, highly electrical conductivity, good catalytic, low cost, and so on.First of all, the anodic coating ofα-PbO2-Co3O4-CeO2 on stainless steel was prepared by DC deposition in this paper. The effect of different conditions and solid particles on the binding, appearance and deposition rate of the composite were researched. The results determined the optimum conditions for electrode preparations: the current density 1.5 A/dm2, electroplating time 2 h, temperature 40℃, and Co3O4 30 g/L and CeO2 15 g/L. SEM,XRD and linear sweep voltammetry(LSV) were used for the analysis of the surface structure, phase composition and oxygen evoluction potential analysis in zinc sulfate electrolyte. The results showed that the particles of depositing can not only improve electrode surface area but also reduce the granularity of pellet. Adding Co3O4 and CeO2 coating electrode restrained the preferential growth and weakened diffraction intensity ofα-PbO2.Theα-PbO2-CoaO4-CeO2 electrode has an lower oxygen evolution potential and higher electrocatalytic activity than PbO2 electrode.With the different dosage of CNT in Pb(NO3)2 electroplating solution,β-PbO2-CNT were prepared on stainless steel/α-PbO2-Co3O4-CeO2 composite coatings. It can be seen from electrochemical analysis that doped with different concentrations of CNT,20 g/L was determined as the optimal doping CNT concentration. It indicates from the anode polarization curves that kinetic parameters a and b values of stainless steel/β-PbO2-CNT composite coating was smaller than that of without adding CNT and has better electro-catalytic activity. Tafel curve shows that the doped CNT can improve the corrosion resistance of the electrode, but the effect is not obvious.It can be seen from cyclic voltammetry that doped CNT does not change the reaction mechanism ofβ-PbO2, the reduction peak is not shifted and reduced. SEM images show that grain morphology ofβ-PbO2 coating without adding CNT was octahedral shape and coarse grains, relatively. The grain surface ofβ-PbO2 coating with CNT was not uniform. There were octahedralβ-PbO2 particles, the CNT distribution surface and the small octahedralβ-PbO2 particles at the surface by the impact of CNT.PbO2 particles were prepared withα-PbO2-Co3O4-CeO2/β-PbO2-CNT Composite coating, then PbO2 particles were pressed into Pb-(1%) Ag anode surface as a new type of anode material, compared to Pb-(1%) Ag anode in zinc electrowinning process, this anode material has lower cell voltage and high current efficiency更多还原