Bai Ruipeng, Lin Yuan, Guo Yuan, Zhang Zhen
Beijing National Laboratory of Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
University of the Chinese Academy of Sciences, Beijing 100049, China.
J Chem Phys. 2022 Jun 21;156(23):234704. doi: 10.1063/5.0093428.
The interfacial structure of a super-concentration LiNO aqueous electrolyte was studied using non-resonant second harmonic generation (SHG) and heterodyne-detected SHG spectra. First, we investigated the electric double layer structure at the air/LiNO interface. As the concentration of LiNO increased, the SHG intensity first increased and then remained unchanged, while the SHG phase changed by about 5°. These results reveal that there was only a small amount of NO at the interface. The increase of the SHG intensity resulted from the thickening of the interfacial water molecular layer. In addition, we studied the broadening mechanism of the electrochemical stability window (ESW) for the super-concentrated LiNO aqueous electrolyte. During cyclic voltammetry scanning, the potential-dependent SHG curves of the Pt/LiNO interface verify that at the cathodic end of the ESW, as the concentration of LiNO increased, the orientation angle θ of Pt-H changed less and the number density N of Pt-H gradually decreased, which indicates the decrease of the number of adsorbed H atoms on the Pt electrode surface. Therefore, the decrease of the number of free water molecules on the Pt electrode surface resulted in an expanded ESW.
采用非共振二次谐波产生（SHG）和外差检测SHG光谱研究了超浓LiNO水系电解质的界面结构。首先，我们研究了空气/LiNO界面的双电层结构。随着LiNO浓度的增加，SHG强度先增加后保持不变，而SHG相位变化约5°。这些结果表明界面处只有少量的NO 。SHG强度的增加是由于界面水分子层增厚所致。此外，我们研究了超浓LiNO水系电解质的电化学稳定窗口（ESW）展宽机制。在循环伏安扫描过程中，Pt/LiNO界面的电位依赖SHG曲线证实，在ESW的阴极端，随着LiNO浓度的增加，Pt-H的取向角θ变化较小，Pt-H的数密度N逐渐降低，这表明Pt电极表面吸附H原子的数量减少。因此，Pt电极表面自由水分子数量的减少导致ESW扩大。
