Unlocking High-Performance Sodium Acetate Trihydrate PCMs via Strontium Chloride Hexahydrate/rGO Synergy: From Mitigated Supercooling to Rapid Phase-Change Kinetics

Abstract

Despite its high energy storage density and low cost, sodium acetate trihydrate (SAT) suffers from severe supercooling and poor thermal conductivity, limiting its practical use as a latent heat storage material. This study demonstrates that the supercooling of pristine SAT can be effectively suppressed from 34 °C down to 4.4 °C by employing a low weight fraction (0.50 wt.%) of SrCl2·6H2O (St) as a heterogeneous nucleating agent. While this binary SAT/0.5St blend experiences a minor ~5% enthalpy drop, the supplementary addition in reduced graphene oxide (rGO) nanoparticles completely recovers this loss. The resulting ternary composite, SAT/0.5St/0.125rGO, achieves an outstanding latent heat of 279.8 J/g, retaining 99.9% of pristine SAT’s capacity (280 J/g). Systematic thermal evaluation demonstrates that the co-addition of St and rGO effectively mitigates supercooling while successfully preserving the pristine latent heat capacity of the SAT matrix. Exhibiting an accelerated temperature response—characterized by a 6 min charging time and a rapid < 1 min discharging phase—this multi-component PCM presents a reliable candidate for advanced thermal engineering applications. Overall, these findings establish the baseline thermal performance for freshly prepared lab-scale samples (10 g for T-history and milligram-scale for DSC) within this specific SAT formulation, highlighting the need for future long-term thermal cycling stability and scale-up studies across broader salt hydrate systems.