双金属氧化物/氮掺杂介孔碳复合结构的构筑及超电容海水淡化性能研究

Capacitive deionization (CDI), as an emerging water treatment technology for desalination, has been rapidly developed over the past decade．Based on stable and porous electrodes with high specific surface area, CDI technology removes ions and leads to water purification through a flow-through capacitor (FTC)．The key component of FTC is the electrodes with high capacitance and adsorption capacity, and it is crucial to develop porous electrode materials with excellent electrochemical and adsorbing performance for the development of CDI technology. The most commonly used electrodes for electrochemical capacitors and CDI technology are carbon-based materials. While the single carbon materials usually lead to poor electrochemical performance and low adsorption capacity, which limit the development of CDI technology. Proper porous size matching with electrolyte ions, N-doping and modification with metal oxides can effectively improve the electrochemical performance and adsorption capacity of carbon-based electrodes. Based on the research situation, this study focuses on the preparation of dual metal oxides-modified N-doping mesoporous carbon electrodes for supercapacitive deionization. It is expected to obtain high effective surface area with suitable mesopore size, which can provide large electric double layer reaction area and a low-resistance diffusion pathway for electrolyte ions. Associated with the enhancement of conductivity and ion carrier property by N-doping, the electrochemical performance can be improved noticeably. Subsequently, dual metal oxides with high pseudocapacitance are designed to modify the as-prepared N-doping mesoporous carbon to generate more activated sites in three dimensions for ion adsorption. Then, supercapacitive deionization electrodes with low cost, high efficiency and stability are designed and prepared. Finally, the supercapacitive deionization modal based on Hybrid capacitance (electrical double layer capacitance-pseudocapacitance) will be constructed. This project will provide new concepts and technical support for controllable preparation of electrodes with excellent supercapacitive deionization performance in large scale and pave way for the efficient utilization of energy.

电容法海水淡化(CDI)是近十余年快速发展的一种用于脱盐的新型水处理技术，基于大比表面积的多孔电极，通过流通电容器实现离子吸附及水的净化。CDI技术的核心是高比电容和大吸附量的电极，因此开发电化学及吸附性能优异的电极材料是CDI技术发展的关键。碳基材料是目前应用最广泛的超级电容器及CDI电极材料，然而单一碳材料比容量及离子吸附率有限。有效孔结构、杂原子掺杂及金属氧化物修饰是提高碳材料超电性能和脱盐性能的有效途径。本研究提出可控构筑双金属氧化物修饰氮掺杂介孔碳结构，通过介孔结构提高碳材料有效比表面积并降低离子扩散阻力，氮掺杂改善材料的导电性和离子传输特性，双金属氧化物修饰提高比电容，激活三维空间离子吸附过程。最终可控制备低成本、高效、稳定的超电容脱盐电极，建立双电层-赝电容混合式脱盐模型，为超电容脱盐电极的宏量制备及性能调控提供理论支持，为能源高效利用提供新思路。

本项目面向国家解决能源问题的战略需求，结合本单位的海洋地域优势及海水淡化技术的迫切需求，围绕电容法海水淡化面临的关键科学与技术问题，力求发展低能耗、高效率的具有自清洁功能的双电层-赝电容混合式超电容脱盐技术。针对目前单一碳脱盐电极性能的不足，本研究构筑了多种多元金属氧化物(硫化物/氢氧化物)/碳复合结构，可控制备低成本、高效、稳定的混合式超电容电极，并设计搭建超电容脱盐系统，发展双电层-赝电容混合式超电容脱盐技术。制备的氮掺杂多孔碳球，0.5 A g-1电流密度下，比电容为244-313 F g-1，且5000次循环后的电容保持率为92.7-93.9%，稳定性优异。以碳球作为模板制备的NiCo2O4电极材料在0.5 A g-1的电流密度下，它表现出了1800 F g-1的高比电容。当电流密度增大到10 A g-1后，比电容仍然高达1320 F g-1。设计新型的双层镍钴前驱体诱导制备的NiCo2S4经过Cu、Fe掺杂改性并与氮掺杂石墨烯复合获得纳米片阵列三维结构在电流强度为10 A·g-1 时比电容可高达2840 F·g-1，为超电容脱盐电极的选择奠定了实验基础。在对一系列电极材料的微观组织结构、组分及电化学性能进行深入分析对比的基础上，分别阐明了多元金属氧化物(硫化物/氢氧化物)/碳复合材料超电容脱盐电极的构效关系、离子吸脱附过程及机理，建立混合式超电容脱盐模型，为海水资源的高效利用提供新思路和技术支撑。