Understanding molecular structure at liquid interfaces is of essential importance for both fundamental and applied sciences. Specifically, molecular level elucidation of electrode/non-aqueous electrolyte solution interfaces is crucial for further development of secondary batteries. Vibrational sum frequency generation is one of the second order nonlinear spectroscopies and provides unique inherent interface selectivity. In particular, heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy enables us to measure not only the intensity but also the phase of the signal light and hence it  provides complete spectral information ( J. Chem. Phys. 130, 204704 (2009).). HD-VSFG has been successfully applied to gas/liquid and transparent solid/liquid interfaces, and it has revealed substantial new knowledges about the structure and dynamics of water at interfaces (Ann. Rev. Phys. Chem. 64, 579-603 (2013), Chem. Rev. 117, 10665−10693 (2017)). However, it is still difficult to realize HD-VSFG measurements at buried electrode/electrolyte solution interfaces. In the present study, we developed a new measurement scheme which realizes HD-VSFG spectroscopy at electrode/electrolyte solution interfaces for studying solvent orientation under the potential control. HD-VSFG spectra of the polycrystalline platinum electrode/acetonitrile solution interfaces revealed that the orientation of acetonitrile strongly depends on the electrode potential as well as the electrolyte in the solution.

Heterodyne-detected vibrational sum frequency generation spectroscopy for buried electrode/electrolyte solution interfaces

255th National Meeting (2018)

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