Time-resolved SERS study of the oxygen reduction reaction in ionic liquid electrolytes for non-aqueous lithium-oxygen cells.
Time-resolved SERS study of the oxygen reduction reaction in ionic liquid electrolytes for non-aqueous lithium-oxygen cells.
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DOI：
10.1039/c7fd00170c
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发表时间：
2018
影响因子：
3.4
通讯作者：
P. Radjenovic;L. Hardwick
中科院分区：
文献类型：
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作者：
P. Radjenovic;L. Hardwick
超氧化物（O2˙-）是非水电解质氧还原过程中形成的关键中间体。实现实用锂氧（Li-O2）电池的一个重要障碍是电解质在自由基氧化物（主要是超氧化物）存在下的不稳定性。在这里，我们使用O2˙-的拉曼活性带作为诊断分子来探测电解质对反应过程和电极表面中间体的影响。采用两种不同性质的离子液体：1-丁基-1-甲基-二氮杂基二（三氟甲烷磺酰基）亚胺（Aze14TFSI）和三乙基磺基二（三氟甲烷磺酰基）亚胺（TESTFSI），前者具有较大的/软阳离子，而后者具有相对较小的/硬阳离子和e-接受阳离子。反阳离子和电位对O2˙-的自由基性质或路易斯碱度有显著影响。分析O2˙相关光谱带的峰强度和Stark位移，可以阐明其特性和电解质相互作用的关键信息。动态表面电位的时间分辨研究允许实时观察电极/电解质界面上离子的通量和重定向。
Superoxide (O2˙-) is the key intermediate formed during oxygen reduction in non-aqueous electrolytes. One significant obstacle towards the realisation of a practical lithium-oxygen (Li-O2) battery is electrolyte instability in the presence of radical oxides, principally superoxide. Here we use the Raman active bands of O2˙- as a diagnostic molecule for probing the influence of the electrolyte on reaction processes and intermediaries at the electrode surface. In situ surface enhanced Raman studies of the interface at a roughened Au electrode with controlled and dynamic surface potentials were performed in two ionic liquids with differing properties: 1-butyl-1-methyl-azepenium bis(trifluoromethanesulfonyl)imide (Aze14TFSI), which has a large/soft cation, and triethylsulfonium bis(trifluoromethanesulfonyl)imide (TESTFSI), which has a relatively small/hard and e- accepting cation. The counter-cation and potential were seen to significantly influence the radical nature, or Lewis basicity of O2˙-. The analysis of peak intensities and Stark shifts in O2˙- related spectral bands allowed for key information on its character and electrolyte interactions to be elucidated. Time-resolved studies of dynamic surface potentials permitted real time observation of the flux and reorientation of ions at the electrode/electrolyte interface.