No abstract

Organic phase change materials (PCMs) have attracted increasing attention in the solar energy utilization field for their large thermal energy storage density, appropriate phase transition temperature, and excellent chemical stability. However, the liquid leakage defect and poor solar-thermal conversion performance restrict their large-scale application. Herein, novel PCM composites with superior solar-thermal conversion efficiency, excellent form-stability, and improved thermal conductivity were successfully synthesized by introducing a dopamine-decorated MXene (Ti3C2T x @PDA) into a poly­(ethylene glycol) (PEG)-based polyurethane PCM. Ti3C2T x @PDA, which was covalently bound to polyurethane, acted as a photon capturer and molecular heater and converted solar energy to thermal energy, whereas the PEG-based polyurethane PCM could absorb and store the generated thermal energy through solid–solid phase transition. Sunlight irradiation experiments demonstrated that the solar-thermal conversion and storage efficiency of PCM composites (up to 90.1%) were significantly improved with the introduction of the MXene Ti3C2T x @PDA. Based on differential scanning calorimetry (DSC) analysis, PCM composites exhibited satisfactory phase change enthalpy in the range of 121.9–128.2 J/g. Moreover, the developed PCM composites possessed excellent form-stability, remarkable thermal reversibility, good thermal stability, and improved thermal conductivity. In conclusion, the synthesized PCM composites exhibited tremendous application potential in solar energy utilization field.

The exploitation of phase change materials (PCMs) with excellent shape stability, considerable latent heat storage capacity, and superior thermal conductivity is essential for their applications in heat storage and thermal regulation. Here, form-stable composite PCMs based on n-octacosane, nanofibrillated cellulose (NFC), and carbon nanotubes (CNTs) were successfully obtained by impregnating n-octacosane into the alkylated NFC/CNTs hybrid aerogels. The three-dimensional interconnected porous aerogels could adequately support the melted n-octacosane and prevent the leakage problem due to strong capillary force and surface tension. After treatment with alkylated modification, the affinity between NFC/CNTs aerogels and n-alkanes was significantly improved, resulting in excellent shape stability, improved thermal reliability, and high n-alkanes loading capacity for the as-prepared composite PCMs. The differential scanning calorimetry analysis showed that composite PCMs based on the alkylated NFC/CNTs aerogels exhibited an extremely high phase change enthalpy ranging from 250.9 to 252.9 J/g. Furthermore, the thermal conductivity and photothermal conversion and storage efficiency of the synthesized PCMs were effectively enhanced by the introduction of CNTs. Thus, the synthesized composite PCMs exhibit considerable potential for practical application in heat storage and thermal regulation.

Flame-retardant PCMs with high energy storage density and superior solar-thermal conversion efficiency were fabricated by impregnating n-octacosane into CNF/BP aerogels.