Structural Study\nof Aqueous Electrolyte Solution by\nMeV Liquid Electron Scattering

The impact of ions on water has long been a subject of\ngreat interest,\nas it is closely tied to the hydration structure, dynamics, and properties\nof electrolyte solutions. Over centuries of investigation, the influence\nof ions on water’s structure remains highly debated. Prevailing\ntechniques, such as neutron and X-ray scattering, primarily focus\non the microscopic structure of salt solutions at very high concentrations,\nmostly above 1 mol/L. In this study, we measured the structure of\naqueous potassium iodide (KI) and potassium chloride (KCl) solutions\nusing MeV liquid electron scattering (MeV-LES) across a concentration\nrange of 0.10 to 0.75 mol/L. The obtained results provide detailed\ninsights into the variations in ion–oxygen and oxygen–oxygen\ncorrelations as a function of concentration. The observed structural\ndifferences between KI and KCl solutions are in line with the structure\nmaker/breaker theory, which suggests that iodide ions exert a more\npronounced effect than chloride ions on disrupting the water shell.\nThis work demonstrates the potency of MeV-LES for investigating the\natomic structure in liquids, augmenting the modern analytical toolbox.