Molecular dynamics study on the effect of surface ionization on the interfacial heat transfer between silica and water

Understanding the thermal transport across the solid-liquid interface is crucial for the advancement of modern technology, with particular emphasis on the silica-water interface due to its universality and remarkable applications in energy conversion and medical treatment. Surface ionization is common for silica surfaces immersed in an aqueous environment, providing an adaptable way to modify silica surface properties. In this study, molecular dynamics simulation was employed to investigate the effect of surface ionization on the interfacial heat transfer between silica and water. It was demonstrated that increasing surface ionization significantly improves interfacial thermal conductance. Interactions between silica and water are strengthened so that more water molecules gather at the interface with higher ionization degree. In addition, increasing ionization results in more hydrogen bonds between ionized silica and water, producing more efficient interfacial heat paths. Somewhat counter-intuitively, although greater surface ionization does result in larger Coulombic forces, the primary contributor to enhanced interfacial thermal conductance is stronger repulsive van der Waals interactions, facilitated by decreased silica-water distances. Overall, this work successfully illustrated the mechanism of interfacial heat transfer enhancement due to surface ionization.