MXene/graphene hybrid nanoparticles for high-efficiency thermal energy storage in metal-organic framework-based phase change composite

This work presents a lauric acid (LA)-based phase change composite (PCC) incorporating a HKUST-1 metal-organic framework (MOF) with a hybrid of low-cost Ti₃C₂ MXene and Graphene to improve its thermal energy storage (TES) performance. The Ti₃C₂ MXene was produced from automobile-derived carbon soot (CS) and aluminum (Al) recovered from discarded beverage cans, which were subsequently combined with graphene at a 1:1 mass ratio. Incorporating 1.25 wt% of HKUST-1 MOF into LA increased the thermal conductivity of LA from 0.198 ± 0.005 to 0.254 ± 0.005 W/mK, exhibiting 28 % enhancement, but reduced the latent heat from 175.6 ± 1.8 to 141.1 ± 2.5 J/g due to partial displacement of active composite. The highest addition of 0.4 wt% MXene: Graphene hybrid nanoparticles (hNPs) into LA/HKUST-1 based PCC-1 system further increased the thermal conductivity to 0.33 ± 0.005 W/mK with 66 % enhancement over LA, recovering and surpassing the latent heat to 182.4 ± 1.6 J/g. Thermogravimetric analysis (TGA) showed improved thermal stability, with the final degradation temperature shifting from 245 °C for LA to 251 °C for the optimized PCC-5. Thermal cycling tests over 100 melting-solidification cycles confirmed excellent retention of latent heat and thermal conductivity, indicating robust long-term reliability. A hotplate step-response experiment further verified the accelerated heat transfer, with the characteristic response time t₉₀ reduced from 42 ± 2 s for LA to 31 ± 2 s for LA/HKUST-1-based PCC-1 and 23 ± 1 s for the fully hybridized PCC-5, consistent with the measured conductivity enhancements. Overall, the results demonstrate a sustainable, scalable, and high-performance TES material suitable for low-temperature solar thermal storage and battery thermal management applications.