铈基液流电池用过渡金属氮化物/石墨毡复合电极材料的可控制备及构效关系研究

Redox flow batteries are used as large-scale electrochemical storage devices to facilitate the integration of inherently intermittent renewable energy resources with the current grid. Specifically, the cerium-based redox flow battery, due to its less harm to the environment, low cost, high cell voltage and energy density, has gained significant interest. However, the poor kinetic reversibility and electrochemical activity of state-of-the-art electrodes toward redox reactions of cerium species remain longstanding barriers for cerium-based redox flow batteries. To this end, present project with the settlement of above-mentioned issues as a starting point, synthesizes transition metal nitride/graphite felt composite electrodes by depositing transition metal oxide precursors on graphite felt substrates with excellent conductivity through solvothermal or electrochemical deposition methods and the sequential controlled nitriding treatment. Then the nucleation, growth and nitridation of transition metal nitride nanocrystal in the preparation process will be systematically investigated. The control methods of composition, morphology, exposed face and other characteristics for the obtained materials, and the correlation of these characteristics with the electrocatalytic performance will be studied. Furthermore, the electrocatalytic mechanism for the electrode materials toward cerium redox couples are analyzed. We intend to provide theoretical and technical guidance for developing a composite electrode with excellent electrocatalytic properties for cerium-based redox flow batteries. This project is a forward-looking study academically associated with related fundamental theories and practical application of electrode materials for cerium-based redox flow batteries.

氧化还原液流电池作为一种大规模的电化学储能装置，可以将间歇性的可再生能源整合到现有的电网。其中铈基液流电池由于其活性物质环境友好、成本较低廉、电压及能量密度高等优异的特性引起了人们的广泛的关注。但铈基液流电池常用的电极材料动力学可逆性与电化学活性较差，限制了电池的性能。本项目以解决上述问题为出发点，拟采用溶剂热或电化学沉积等方法，在具有优良导电性的石墨毡基底材料上原位负载过渡金属氧化物前驱体，进而通过后续的受控氮化处理制备过渡金属氮化物/石墨毡复合材料，系统分析过渡金属氮化物纳米晶体制备过程中成核生长规律和氮化机制，研究纳米晶体的组成、形貌和暴露晶面等参数的调控以及它们与电催化性能之间的相关性，探讨催化反应机理，为构建性能优异的铈基液流电池电极材料奠定坚实的理论和技术基础。本项目内容具有研究方向前沿性和应用基础意义。

铈基液流电池由于其高电压及高能量密度的优势，在大规模储能领域有着广泛的应用前景。为获得高性能的铈基液流电池，发展高电化学性能的电极材料是当前的一个研究热点。在本项目中，项目组在石墨毡表面原位负载氮化钼、氮化钨或氮化铌纳米结构来制备复合电极材料，以提高石墨毡的电化学活性，获得高性能的铈基液流电池。主要研究内容包括：（1）采用浸渍或水热反应方法在石墨毡表面原位生长氧化钼、氧化钨、氧化铌纳米晶，通过对形核-生长过程的调控，实现纳米晶微结构的可控制备，优化制备出纳米墙阵列结构。（2）以氧化物为前躯体，通过调控还原氮化反应的热力学和动力学过程，制备氮化钼、氮化钨、氮化铌纳米墙阵列，制备的氮化物纳米结构具有超高的亲水性。（3）氮化物纳米墙阵列结构可以与电解液充分接触，充分暴露活性位点用于催化反应，同时氮化物的超亲水性、高导电性可以促进铈电对电极反应过程中的电荷转移，以上因素协同作用，提高了铈基液流电池的性能。在40 mA cm-2的充放电速率下，电池的能量效率提高了46.8%。并且，对电极反应中的催化机理进行了研究和分析，建立了催化剂材料的构效关系。此外，还开发了新型全流动的铈-金属液流电池系统；采用直接热裂解法或金属有机碳骨架化合物衍生法在石墨毡表面生长氮掺杂纳米管催化剂，并确定了其对铈电对氧化还原反应的确切催化位点；通过在电解液中添加L-半胱氨酸来对石墨毡进行三官能团的掺杂，通过以上研究来进一步地提高铈基液流电池的性能和拓展其应用领域。