Wettability of molten sodium sulfate salt on nanoscale calcium oxide surface in high-temperature thermochemical energy storage

Abstract Molecular dynamics simulations were carried out to originally investigate wettability of molten sodium sulfate salt on nanoscale calcium oxide surfaces at high temperature and micro-mechanisms on the molten salt promoting the performance of thermochemical energy storage. It was found that in terms of the molten sodium sulfate salt, the nanoscale calcium oxide surface was hydrophilic, and became more and more hydrophilic with increasing temperatures. More importantly, average diffusion coefficients and radial distribution functions of various ions illustrated that the molten sodium sulfate activated the calcium ions and the oxygen ions on the calcium oxide surface, resulting in weak fluidization of the surface at a temperature below the melting temperature. This promoted potential energy of the atom interaction at the contact interface. Additionally, it was observed that the sodium sulfate transited from partial coverage to complete coverage on the spherical nanoscale calcium oxide surface. Higher temperatures induced better coverage performances due to the decreasing surface tension of the molten salt. Therefore, the molten salt formed a screen on the surface to effectively prevent the calcium oxide particles from sintering. This study provides a theoretical foundation to further utilize the molten salt to promote the performance of the thermochemical energy storage.