Hydrogen bond network at the H₂O/solid interface

Probing the chemical, structural, and electronic properties of dynamically evolving H2O/solid interfaces is highly desirable due to the ubiquity of such interfaces in numerous fields. Ambient pressure X-ray photoelectron spectroscopy (APXPS) has been used in a wide range of studies to investigate the microscopic details of the H2O/solid interface, in particular, the hydrogen bond network that develops as water builds up on top of the material surface. Here, we review the fundamentals of APXPS, recent advances in the instrumentation, and its scientific applications in studying the properties of water on various surfaces. We discuss cases where the thickness of H2O layer varies between one monolayer and tens of nanometers, as the thickness of water plays a critical role in determining the properties of the interface. In addition, we discuss computational approaches based on density functional theory (DFT) that can be used to model (AP)XPS spectra, support spectral peak assignments, and provide information beyond what can be readily obtained experimentally.