Lightweight polypyrrole/MXene-integrated melamine foam/polyethylene glycol composite for efficient thermal energy storage, photothermoelectric conversion, and microwave absorption

Traditional phase change materials (PCMs) for thermal energy storage face critical limitations such as low thermal conductivity, leakage in the liquid phase, and insufficient solar energy harvesting capability, which hinder their efficiency and broader application. This study innovatively employs lightweight three-dimensional porous melamine foam (MF) as a scaffold. Through impregnation and in-situ polymerization processes, MXene and polypyrrole (PPy) nanoparticles are incorporated into the foam to construct a functionalized carrier (MF/MXene-PPy). Subsequently, vacuum impregnation technology was employed to efficiently load polyethylene glycol (PEG) with a mass fraction as high as 97.74% as the heat storage medium, ultimately yielding a composite phase change material (CPCM) that integrates thermal energy storage, photothermoelectric conversion, and microwave absorption capabilities. The resulting PEG@MF/MXene-PPy CPCM demonstrates exceptional thermal storage performance, with melting enthalpy and crystallization enthalpy reaching 162.18 and 153.74 J·g −1 , respectively. In terms of photothermal performance, the PEG@MF/MXene-PPy composite achieves a photothermal conversion efficiency of 96.42% due to the localized surface plasmon resonance effect of MXene and the broad-spectrum absorption capability of PPy nanoparticles. Additionally, the material shows excellent microwave absorbing performance, with a minimum reflection loss of −36.69 dB at 15.94 GHz with a 2.1 mm matched thickness. After 100 thermal cycles, the composite maintains dimensional stability and high enthalpy retention. This work provides a novel paradigm for the design of multifunctional PCMs, offering great potential for applications requiring synchronized energy storage, solar-thermal-electric conversion, and electromagnetic interference shielding.