The interfacial structure of super-concentration LiNO3 aqueous electrolyte studied by second harmonic generation

Abstract

Using non-resonant second harmonic generation (SHG) and heterodyne-detected SHG (HD-SHG) spectra,we studied the broadening mechanism of the electrochemical stability window (ESW) for the super-concentrated LiNO3 aqueous electrolyte. We first investigated the electric double layer structure at the air/LiNO3 interface. As the concentration of LiNO3 increased, the SHG intensity first increased and then remained unchanged, while the SHG phase changed by about 5{degree sign}. These results reveal that there was only a small amount of NO3− at the interface. The increase of SHG intensity resulted from the thickening of the interfacial water molecular layer. We then studied the mechanism of the ESW. During cyclic voltammetry scanning, the potential-dependent SHG curves of the Pt/LiNO3 interface verify that at the cathodic end of the ESW, as the concentration of LiNO3 increased, the orientation angle θ of Pt-H changed less and the number density Ns of Pt-H gradually decreased, which indicates the decrease of the number of adsorbed H atoms on the Pt electrode surface. The conclusion is that the decrease in the number of free water molecules on the Pt electrode surface results in an expanded ESW.

In Situ Heterodyne-Detected Second-Harmonic Generation Study of the Influence of Cholesterol on Dye Molecule Adsorption on Lipid Membrane

“…The total SHG intensity, I SHG , is given by I SHG ∝ | E sam ( 2 ω ) + E ref ( 2 ω ) | 2 = | E sam ( 2 ω ) | 2 + | E ref ( 2 ω ) | 2 + 2 E sam ( 2 ω ) E ref ( 2 ω ) α cos ⁡ Φ where α is the overlap parameter that represents the degree of spatial and temporal overlap, and Φ is the overall phase. Φ can be obtained by fitting the interference pattern with the following equation: I SHG = I 0 + A cos false( f x + φ fit false) where x is the stage position, and I 0 , A , f , and φ fit are fitting parameters.…”

“…The total SHG intensity, I SHG , is given by where α is the overlap parameter that represents the degree of spatial and temporal overlap, and Φ is the overall phase. Φ can be obtained by fitting the interference pattern with the following equation: where x is the stage position, and I 0 , A , f , and φ fit are fitting parameters.…”

“…Polarization SHG and HD-SHG were conducted using a typical reflective configuration. , In brief, the incident beam, centered at 800 nm, was generated by a broadband tunable mode-locked femtosecond Ti:sapphire oscillator (Tsunami 3960C, Spectra-Physics). The SHG signal, generated by the sample, was passed through an off-axis parabolic mirror (MPD149-F01, Thorlabs).…”

Probing the adsorption configuration of methanol at a charged air/aqueous interface using nonlinear spectroscopy

“…It has been reported that the surface potential at the air/ aqueous interface can be determined using HD-SHG. [38][39][40]74 When the surface potential is opposite at the air/aqueous interface, the j sig should also be opposite. As shown in Fig.…”

“…In addition, nonlinear spectroscopy heterodyne-detected second harmonic generation (HD-SHG), a special SFG process, is also a powerful tool to investigate ion specificity at the electrical double layer of the charged interface using the new w (3) model. [37][38][39] Bai et al 40 also investigated the electric double layer structure at the super-concentrated air/LiNO 3 aqueous electrolyte interface using HD-SHG. With the intrinsically interfacial sensitivity and selectivity SFG technique, Shen initially reported the molecular structure of methanol at the air/neat methanol interface, 41 and subsequently the methanol/water mixture interface was extensively studied.…”