催化有机相中氧还原的酶电极及其应用于锂空气电池的研究

Recently, rechargeable Li-air batteries have attracted much attention because of their extremely high theoretical specific energy. However, the sluggish oxygen reduction reaction (during discharging) and oxygen evolution reaction (during charging) in organic electrolyte lead to the large overpotentials and the low round-trip efficiency of nonaqueous Li-air batteries, which is closely related to the electrocatalytic activities of air electrodes. It is well-known that enzymes dramatically increase the rate of the reaction and are highly specific for their substrates, which make some enzymes be the possible catalyst candidates of increasing the rate of oxygen reduction reaction and reducing the side-reactions in nonaqueous Li-air batteries. In this project, highly stable enzyme electrodes based on laccase or bilirubin oxidase will be firstly constructed by hydrogel or sol-gel immobilization. Then, the possibility, catalytical activity,and mechanism of enzyme electrodes towards catalyzing oxygen reduction reaction in organic phase will be investigated in a systematic way. Finally, the application of enzyme electrodes as air electrodes of nonaqueous Li-air batteries will be investigated. We expect that this project in the one hand could extend the applications of enzyme electrodes, in the other hand could be beneficial to the development of the future high-performance Li-air batteries.

最近，拥有极高理论比能量的锂空气电池吸引了广泛的研究兴趣。有机相中氧气还原反应（放电时）和氧气析出反应（充电时）的低反应速率导致了有机体系锂空气电池存在着充放电过电势大、充放电效率低等瓶颈问题，这与空气电极的催化活性密切相关。酶催化反应具有催化效率高、高度专一性等特点，有望解决锂空气电池放电过程中氧气还原反应速率低、副反应多的问题。在本项目中，我们拟首先通过水凝胶或溶胶-凝胶固定等方法构建基于漆酶或胆红素氧化酶的高稳定性酶电极，然后深入研究酶电极在有机溶剂中催化氧气还原的可行性、催化性能、机理及各种实验条件（包括电极制备方法、溶剂等）的影响，最后探索酶电极作为空气电极在有机体系锂空气电池中的应用及其构效关系。本项目的实施既大大拓展了酶电极的应用范围，也为未来高性能锂空气电池的研发提供了理论依据。

因具有非常高的理论能量密度，非质子溶剂锂空气电池近年来吸引了越来越多的研究兴趣。但是现有的锂空气电池普遍存在充放电极化大、循环性能差等关键问题，严重限制了锂空气电池的快速发展。大量研究表明，阴极催化剂的使用可以有效降低充放电极化并提高循环性能。因此，高性能阴极催化剂的合理设计和优化对于锂空气电池来说至关重要。本项目主要发展了酶基及过渡金属基催化剂新材料，开展了电极/电解液界面稳定性研究，实现了锂空气电池性能的有效提升。本项目主要取得了如下重要进展：（1）以水凝胶为载体，开发了基于漆酶及胆红素氧化酶的酶基催化剂体系，考察了酶电极对有机相中氧气还原反应的催化性能及各种实验参数对酶电极催化性能的影响；继而以酶电极作为空气电极应用于有机体系锂空气电池，构建了基于生物阴极的锂空气电池，虽充放电比容量较低且容量衰减较快，但实现了多个循环的充放电。（2）开发了多种高性能过渡金属氮化物/氧化物阴极催化剂新材料，有效降低了电池的充放电极化，提高了其循环稳定性；为深入研究基于该类催化剂的锂空气电池的充放电可逆性，发展并运用先进的电化学原位质谱技术对使用NiCo2O4催化剂的锂空气电池的充放电过程进行了原位表征，发现阴极上的充放电过程并不遵从理想的Li-O2反应，阐释了钴基氧化物催化剂能够提升电池性能的工作机制，为新型催化剂的设计和开发提供了有益借鉴。本项目为理解非质子溶剂中的氧气电化学提供了新见解，也为高比能、高稳定性锂空气电池的研发提供了一定的基础。