Enhancement of Molten Nitrate Thermal Properties by Reduced Graphene Oxide and Graphene Quantum Dots

Eutectic molten salts are the most studied medium-high temperature thermal energy storage material due to their potential use in concentrated solar power plants. The aim of this work is to investigate the effect of using reduced graphene oxide (RGO) and graphene quantum dots (GQDs) on the thermal properties of eutectic molten salts. A binary nitrate eutectic mixture of NaNO3 and KNO3 was selected as a base material (BM) for nitrate/carbon-derivative composites. RGO and GQDs were individually mixed with the BM with different fractions ranged from 0.1 to 1.5 wt %. The results showed that RGO enhanced the thermal conductivity, heat of fusion, and total thermal energy storage capacity by 52.10%, 44.48%, and 10.44%, respectively. GQDs slightly improved the specific heat capacity for both solid and liquid phases by 2.53% and 3.13%, respectively. In addition, GQDs promoted the heat of fusion by 31.72% and raised the total TES capacity by 12.26%.