锂金属-氧气电池的现场谱学电化学研究

氧气的还原反应是许多电化学技术的基础，如燃料电池、金属-氧气电池。有机电解液锂-氧电池的理论能量密度十倍于锂离子电池，因此它近年来受到广泛的关注。它的工作原理如下，放电时，氧气被还原，固态产物沉积于多孔电极内；充电时，放电产物被分解，氧气释放。其中，氧还原反应的机制决定着电池的实际能量密度、功率密度及电池寿命。最近，申请人提出了利用水和可溶性催化剂/固体金属催化剂的协同作用，来调控氧还原的电化学过程；电池的性能因此大大提高。为了从分子层面进一步理解这些电池体系中氧还原反应的特征，本项目提出借助现场光谱技术（表面增强红外吸收光谱、壳孤立颗粒增强拉曼光谱、超快激光瞬态吸收光谱）研究氧还原中间产物的热力学特征、以及他们之间转化反应的动力学参数。对上述系统的研究，有助于确认并最终理性设计能左右电池性能的物理化学参数。这些利用原位光谱研究氧还原反应的方法对于研究氮气、二氧化碳的电催也有借鉴意义。

The oxygen reduction reaction (ORR) forms the basis of several crucial electrochemical devices, such as fuel cells, metal-oxygen batteries, etc. Because of the high theoretical energy density (10 times of the state of the art Li ion batteries), non-aqueous Li-O2 batteries have garnered tremendous interests from both academia and industry. It typically works as follows: on discharging, oxygen is reduced, solid discharge products precipitating out and depositing on the porous oxygen electrode; on charging, the solid product is decomposed, oxygen being released. The mechanism of the ORR determines the practical energy/power densities and the life-span of the battery. Very recently, the applicant proposed that one can use the synergistic effects between water and redox mediators/metal catalysts to optimize the discharging process, and as a result the battery performance is significantly improved. To develop a deeper understanding at the molecular level, it is proposed in this project that we use operando spectroelectrochemical techniques (Surface Enhanced Infrared Absorption Spectroscopy, Shell Isolated Particle Enhanced Raman Spectroscopy， Ultrafast Laser Transient Absorption Spectroscopy) to study the aforementioned systems, with the aim to identify the reaction intermediate species and analyze their thermodynamic characteristics and reactions kinetics. The fundamental understanding gained by conducting this proposed study will help lock down and eventually rationally design the physicochemical parameters that decide the battery performance. In addition, the operando methodology developed in this project can be applicable to studying the electrocatalysis of other important molecules, such as N2 and CO2.