In the realm of energy research, understanding the behavior of hydrogen bonds is crucial, as they play a significant role in various energy-related processes, from water desalination to energy storage. A team of researchers from the University of Southern Denmark, including Frederik Zysk, Ana Vila Verde, Naveen K. Kaliannan, Kristof Karhan, and Thomas D. Kühne, has delved into the intricacies of hydrogen bonds at the water/air interface, shedding light on how their strength and dynamics can be predicted using experimentally measurable observables.
The researchers employed advanced simulation techniques, specifically path-integral molecular dynamics and electronic structure-based energy decomposition analysis (EDA), to connect hydrogen bond strength, asymmetry, and total delocalization energy to observable phenomena. Their findings, published in the journal Physical Chemistry Chemical Physics, reveal a red-shift in the sum-frequency generation (SFG) spectrum from the interface to the bulk of the water, with a strongly bonded water peak observed at around 3250 cm⁻¹ in the layer closest to the bulk.
The study also found that the reorientation dynamics of water molecules slow down from the interface to the bulk, correlating with the SFG results. Through their EDA, the researchers observed a strong decline in total delocalization energy from the bulk to the interface, as well as a decline in the strength of the strongest donor and acceptor interactions. The asymmetry between these interactions increases towards the interface, while the importance of interactions from the outer solvation shells diminishes.
One of the key findings of this research is the strong correlation between the strength of the strongest hydrogen bond donor/acceptor and the local minimum of the autocorrelation function resembling the L2 band librational motions. This led the researchers to propose a simple yet quantitative relationship between hydrogen bond strength and short-time reorientation dynamics at the water/air interface. This relationship could potentially be extended to predict hydrogen bond strength in other hydrophobic systems from experimentally obtainable observables.
The practical applications of this research for the energy sector are manifold. Understanding and predicting hydrogen bond strength can aid in the development of more efficient water desalination technologies, improve the design of energy storage systems, and enhance the performance of various energy-related processes that involve water interfaces. By providing a clear link between hydrogen bond strength and measurable observables, this research offers valuable insights that can drive innovation in the energy industry.
Source: Physical Chemistry Chemical Physics, 2023.
This article is based on research available at arXiv.