Design and application of polyurethane-polydopamine/Ag double-shell microcapsules for enhanced photothermal conversion and incremental energy storage

Solar energy is a clean and renewable source of energy. However, its intermittent nature hampers its utilization efficiency. Although phase change microcapsules store and release energy using latent heat, they rely on temperature differences, which limits their effectiveness in absorbing and utilizing solar energy as heat. This study employed a two-step method to synthesize a novel double-shell phase change microcapsule to enhance the conversion and step-by-step storage of solar energy. The double shell was constructed using polyurethane (PU) and polydopamine/silver (PDA/Ag), while octadecane and paraffin (P/O) served as the core materials. The synthesized microcapsules displayed a unique double-shell structure, and a consistent spherical shape, and demonstrated a remarkable latent heat storage capacity surpassing 150 J/g. The coating exhibited outstanding photothermal conversion performance, attributed to the synergistic photothermal conversion effect of PDA and Ag in the first shell. The gradual energy transfer within microcapsules was achieved by integrating polyethylene glycol into the PU layer and utilizing two different PCMs as the core materials. Furthermore, the antimicrobial of the treated textiles against S. aureus and E. coli were 99.99% and 99.56%, respectively. The double-layer design of the P/O@PU@PDA/AgNPs provides leakproofness and shape stability, making them ideal for photothermal energy storage applications.