碳纳米管增强铅基阳极机理及其析氧行为研究

The conventional lead alloy anode in zinc electrowinning consume large energy due to the high overpotetnial of oxygen evolution, which is against energy saving and emission reduction. Therefore, the key to decrease energy consumption is to improve catalytic activity of anode. This project combines the special feature of carbon nanotubes(CNTs) including high electrochemical activity, high strength and high electron conduction and so forth with the advantages of conventional lead alloy anode such as robustness and low cost. Mechanism of interfacial bonding between the decorated CNTs and lead is investigated. This project focuses on the problem of composite material between CNTs and lead about large difference of density and size. The wetting properties between metal and non-metal are discovered by both molecular orbital theory and DFT, with the purpose of uniform distribution of CNTs in lead matrix and controllable fabrication of CNTs reinforced lead anode. The Real-time Fourier Transform Electrochemical Impedance Spectroscopy (FTEIS) combined staircase cyclic voltammetry experiments are employed to obtain a large body of electrochemical data acquired from the electrode/electrolyte interface at different Fermi levels. The electrochemical catalytic characters of CNTs in lead composite anode and the relationship between decorated CNTs and behavior of anode are explored. Eventually, the fundamental theory and key methods of controllable fabrication of CNTs reinforced lead anode will be founded. Research fruits will supply theoretical basis for comprehensive utilization of nanotechnology in metallurgical electrowinning.

锌电积过程中使用的传统铅基阳极由于其析氧超电势高导致高能耗，不利于生产过程节能减排，因此，提高阳极催化活性成为降低能耗的关键。本项目基于碳纳米管的高催化活性、高比强度和高导电性以及铅阳极的稳定性、低成本等优势，探索碳纳米管表面修饰机制，利用分子轨道理论和第一性原理揭示出碳纳米管与金属铅界面润湿规律，解决碳纳米管和金属铅和结合存在的高比重差、大尺寸比例问题，实现碳纳米管在金属铅中弥散分布和碳纳米管增强铅基复合阳极可控制备；利用实时快速傅里叶变换电化学交流阻抗联用伏安等电化学技术，获得不同费米能级下的界面电化学参数，探究碳纳米管在阳极过程中的作用机制和催化行为特征，阐明碳纳米管表面修饰与复合阳极析氧行为的内在关联。最终建立碳纳米管增强铅基复合阳极制备的关键方法和基础理论，研究成果为纳米技术在冶金电积过程中的应用提供理论支持。

针对锌电积过程中使用的传统铅基阳极的不足，本项目研究了碳纳米管（CNTs）作为增强相掺杂铅基阳极的制备工艺、机理和电催化性能。研究确定并优化采用复合电沉积的方式制备具有“剑-鞘”结构的CNTs/Pb复合粉体。讨论了碳纳米管预处理方式及浓度、添加剂种类、电解液组元、电解液pH、电流密度、明胶浓度、乙酸铅浓度和超声波功率对电沉积粉体电流效率、粒度、氧化度及电催化性能的影响规律，深入探讨电沉积过程中PbO形成的规律，并构建其形成过程的特征模型。采用高分辨透射等现代分析技术对金属铅与碳纳米管的界面结合进行了深度剖析，结合电化学方法，以理解其原位成核机理，并提出碳纳米管表面包覆金属铅的基本模型。研究了采用粉末冶金技术制备CNTs/Pb复合阳极工艺和规律，探讨了粉末冶金工艺参数如成形压力、烧结气氛、烧结温度和成形时长对CNTs/Pb复合阳极电催化性能的影响规律，在模拟工业锌电积条件下进行了耐蚀性测试，并与工业常用的铅银阳极进行了对比研究。研究了表面官能团化的CNTs、多壁碳纳米管、单壁碳纳米管、富勒烯球和石墨烯等纳米碳材料作为催化增强相制备铅基复合阳极，以及将杂多酸、MnO2、MAXene等与碳纳米管和铅掺杂制备复合材料作为锌电积中的阳极，对复合材料的电催化活性和长期耐久性，以及反应中间体的吉布斯能垒进行分析，探索其在高酸性的锌电积液中的催化稳定性和氧析出反应活性。结果表明使用碳纳米管及其复合材料制备的铅碳复合材料有望替代传统铅银合金阳极，从而为铅合金阳极的发展开辟新的途径。本项目也将傅里叶变换电化学交流阻抗技术（FTEIS）升级为小波变换交流阻抗技术（WTEIS），新技术可以弥补商用电化学工作站的不足，更适用于锌电积在线监测，以实现高电流密度等极端条件下的快速阻抗测量，对于原位实时在线研究铅阳极的电极表面状态提供了有力的工具，对未来冶金电化学过程的自动化控制和监测意义重大。