Synergistic Enhancement of Thermal Energy Storage in Ternary Alkali Metal Carbonate via Hybrid SiC–SiO2 Nanoparticles: An Experimental and Molecular Dynamics Study

To meet the demands of next-generation CSP systems, this study developed a hybrid SiC–SiO2 nanoparticle-doped Li2CO3–K2CO3–Na2CO3 molten salt and systematically evaluated its thermophysical properties through experiments and molecular dynamics simulations. At an optimal doping concentration of 1.5 wt %, the molten salt doped with hybrid SiC–SiO2 nanoparticles exhibited significantly enhanced thermophysical properties: the specific heat capacity increased to 2.33 J·g–1·K–1 (a 38.92% enhancement compared to the base salt), the volumetric heat storage density reached 1.98 GJ·m–3 (+48.87%), and the thermal conductivity improved to 0.98 W·m–1·K–1 (+69.23%). In addition, the operational temperature range was broadened by 23 K, and the average optical absorption was enhanced by approximately 16-fold. Compared to single SiC or SiO2 systems, the hybrid exhibited superior performance. Molecular dynamics simulations further determined that the presence of hybrid nanoparticles enhanced the Coulombic and van der Waals interactions at the interface, promoting the adsorption of ions and the formation of a compression layer. These interfacial effects reconstructed the microstructure and energy distribution of the molten salt, synergistically boosting its thermal capacity. Moreover, the hybrid system demonstrated remarkable dispersion stability and efficient photothermal conversion, positioning it as a strong candidate for advanced thermal energy storage in CSP applications.