The key role of hydroxyl in thermal transport at the silica-water interface: A molecular dynamics simulation

A comprehensive understanding of thermal transport across solid-liquid interfaces is crucial for enhancing the performance of micro- and nanoscale devices, especially at the silica-water interface, which plays a key role in many applications in energy conversion and medical technologies. The adsorbed water layer at the silica interface plays a core role in solid-liquid interface thermal transport. However, the molecular-level structural transitions of this layer and their correlation with thermal transport mechanisms have not been extensively studied. In this work, molecular dynamics simulations were used to study the thermal transport mechanisms at silica-water interfaces with different hydroxyl densities, focusing on how interfacial H-bonds and layered structures influence interfacial thermal transport characteristics. The results of the study show that the interfacial thermal conductance increases with the hydroxyl density, while the density distribution of water molecules at the silica interface shows an opposite trend. The formation of H-bonds at the interface is identified as the main cause of this anomalous behavior. Through density, charge, H-bonds, and water molecule orientation distribution, the bilayer structure of the adsorbed water layer at the silica interface was defined at the molecular level, which is composed of the binding interface layer and the diffuse layer. The binding interface layer plays a decisive role in interfacial thermal transport. Through the analysis of interfacial potential energy, H-bonds dynamics, and Vibrational density of states, the microscopic mechanisms of thermal transport at silica-water interfaces with different hydroxyl densities were proposed by this work. These findings may provide new insights into the understanding of thermal transport mechanisms at solid-liquid interfaces.