Novel organically modified disodium hydrogen phosphate dodecahydrate-based phase change composite for efficient solar energy storage and conversion

Abstract

Disodium hydrogen phosphate dodecahydrate (Na2HPO4•12H2O, DHPD), a typical inorganic hydrated salt phase change material (PCM), is widely utilized for thermal energy storage. However, the key challenges such as significant supercooling, easy phase separation, easy leakage, and limited photothermal conversion capability restrict its actual application. Herein, polyethylene glycol (PEG) was adopted for the first time as a nucleating agent to suppress or eliminate the supercooling degree of DHPD. The inclusion of ultraviolet light-curable polyurethane acrylate (UV-curable-PUA) as an encapsulation medium effectively addresses issues related to phase separation and easy leakage within the DHPD-PEG PCM (DHPDP). In addition, polydopamine (PDA) was introduced as a proficient solar absorber to significantly augment the photothermal conversion performance of DHPDP@PUA/PDA phase change composites (DPPCCs). The results demonstrate that the addition of 2% PEG4000 can effectively minimize the supercooling degree of DHPD to 0.37 °C. Moreover, DPPCCs exhibit favorable tensile strength (1.9 MPa) and elongation at break (31.1%). Remarkably, after undergoing 200 cycles, the enthalpy only decreases by 2.6%. Furthermore, the photothermal conversion performance of DPPCCs is significantly enhanced compared to DHPDP@PUA. In conclusion, the prepared DPPCCs hold great promise for efficient thermal energy storage.