Urea-Derived Graphitic Carbon Nitride/Polyethylene Glycol Form-Stable Composite for Thermal Energy Storage

A novel form-stable phase change material (FSPCM) composed of graphitic carbon nitride (g-C3N4) as the supporting porous medium and polyethylene glycol 2000 (PEG-2000) as the organic phase change material (OPCM) was prepared and comprehensively investigated in the present work. Scanning electron microscopy (SEM) analysis specified that g-C3N4 had distinct pores, which are adequate to enclose the molten PEG-2000 without any seepage. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques validated the chemical agreement of PEG-2000 and g-C3N4. Differential scanning calorimetry (DSC) analysis indicated that the FSPCM having 80 wt % PEG-2000 had melting and solidifying temperatures of 54.77 and 27.60 °C, respectively, and the corresponding latent heat values were noted as 135.02 and 136.90 J/g, respectively. The durability examination for 1000 melting/freezing cycles established that the structural and thermal durabilities are outstanding. Due to the incorporation of g-C3N4 in the FSPCM, thermal conductivity was increased by 117%, which improved the heat transfer rate, and the charging/discharging times of the prepared composite were reduced by about 32–48% in comparison to those of pure PEG-2000. All obtained results exhibited that the produced g-C3N4/PEG-2000 (80 wt %) FSPCM can be considered as a significant material for thermal energy storage (TES) in various applications such as space heating, solar water heating, and thermal maintenance of electronic and automotive units.