Enhanced stimulated Raman scattering of water by KOH

Abstract

Stimulated Raman scattering (SRS) of water and a 1 M KOH–H2O solution are investigated using a Nd:YAG laser in both forward and backward directions. An obvious enhanced SRS signal is realized by dissolving KOH in liquid water. Compared with pure water, the performance improvements include the appearance of low-wavenumber Raman peaks, higher Raman intensity, an increased Raman gain, and an enhanced hydrogen bonding network. In this paper, the SRS enhancement phenomenon is explained from both the hydrogen bonding structure and the mechanism of stimulated Raman scattering. We consider it to be a very important SRS enhancement technique, which is low cost, simple, but reliable. Meanwhile, it can easily be extended to other alkali hydroxides.

Various states of water species in an anion exchange membrane characterized by Raman spectroscopy under controlled temperature and humidity

“…Although the presence of an alkaline solution has been found to lead to an enhanced H-bonding network in water, 46 B6 (3600 cm −1 ) in Fig. 9 representing non-H-bonded water 29,48,51,73 initially dropped slightly on the introduction of KOH at 1.0 M but then increased steadily with concentration almost to the initial level.…”

“…47 This shift towards lower wavenumbers by up to 150 cm À1 in the OH region was attributed to the combined effect of liquid water confinement 69,78 and the enhanced H-bonding network in the alkaline environment. 46 This phenomenon in other AEMs will be studied in the future.…”

“…42 Several researchers have studied water molecules in alkaline solutions using Raman spectroscopy. 43–47 Corridoni et al , while studying OH − stretching band dynamics in LiOH, NaOH, and KOH solutions, were among the first to observe that five Gaussian bands were sufficient to describe the OH stretching region of the aqueous hydroxides. 45 Sbroscia et al , 47 in a similar study in LiOH, NaOH, and KOH hydroxide solutions of different concentrations, also effectively used five bands identical to those reported by Corridoni et al They selected Bands (I) to (IV) to best reproduce the O–H stretching region, while band V, located between 3610 and 3640 cm −1 , was ascribed to the hydroxide anion (Table 1).…”

“…Recently Wang et al observed that the presence of KOH in water led to higher Raman intensity, the appearance of low-wavenumber Raman bands, and an enhanced hydrogen bonding network. 46…”

Role of water structure in alkaline water electrolysis

“…These electric fields polarize the water molecules, resulting in more H-bonding between them. Hence, more tetrahedrally coordinated water molecules are formed with increasing KOH/NaOH/RbOH concentrations (Wang et al, 2020).…”