Synthesis and Characterization of Enhanced Binary Carbonate Molten Salts Using Hybrid Nanoparticles (Al₂O₃–ZnO)

Efficient thermal energy storage (TES) is necessary for the reliability of renewable energy systems, with molten salts recognized as effective high-temperature heat-transfer and storage media. This study examines the improvement of binary carbonate molten salts through the addition of Al₂O₃–ZnO hybrid nanoparticles produced via a one-step synthesis method. Two formulations have been created: a base mixture of Na₂CO₃ and K₂CO₃ (Sample 1) and a modified composition incorporating 0.5 wt% Al₂O₃–ZnO nanoparticles (Sample 2). The samples went through controlled stirring, evaporation, drying, and grinding, followed by comprehensive characterization utilizing Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Ultraviolet–Visible (UV–Vis) spectroscopy. The SEM analysis of Sample 2 demonstrated the presence of finer, needle-like structures characterized by an increased surface area and uniform dispersion of nanoparticles, which enhances heat conduction efficiency. FTIR confirms retention of the carbonate structure with strengthened metal–oxygen interactions, while Sample 2 shows up to 12–15% higher transmittance and an overall 6–8% increase relative to sample 1. UV–Vis results further reveal enhanced transmittance (up to 10–15%) accompanied by a marked 85–95% reduction in absorbance, indicating reduced agglomeration. The findings indicate that the addition of Al₂O₃–ZnO hybrid nanoparticles significantly improves the thermal stability, heat transfer properties, and energy-storage capacity of binary carbonate molten salts, highlighting their applicability in advanced solar-thermal thermal energy storage systems.