Polypyrrole-coated expanded graphite-based phase change materials for photothermal energy storage

Pristine organic phase change materials (PCMs) suffer from liquid leakage and weak solar absorption in solar energy utilization. To address these deficiencies, we prepared polypyrrole (PPy)-coated expanded graphite (EG)-based composite PCMs for photothermal conversion and storage through chemical polymerization and physical infiltration methods. As dual high-efficiency photonic harvesters and molecular heaters, the synergistic integration of PPy and EG significantly boosts the photothermal conversion and storage capability of polyethylene glycol (PEG). The melting enthalpy and solidification enthalpy of PEG@EG/PPy composite PCMs are 148.3 and 141.5 J/g, respectively. Additionally, PEG@EG/PPy composite PCMs also exhibit superior shape stability and latent heat storage retention after undergoing 200 melting-freezing cycles. This convenient strategy sheds light on the large-scale development of high-performance carbon-based photothermal composite PCMs, showing great potential in solar energy utilization.