Hierarchical 3D microencapsulated phase change composites via synergistic dual-encapsulation strategy for advanced thermal management and solar-thermal-electricity conversion

Phase change materials (PCMs) show great promise for thermal management and solar energy harvesting, but their practical applications are hindered by liquid leakage, low thermal conductivity and weak optical absorption. Herein, we report a series of multifunctional composite PCMs engineered via a synergistic dual-encapsulation strategy. The interfacial assembly of TEMPO-oxidized cellulose nanofibrils (TOCN) and graphene oxide (GO) on the n-docosane droplet surface is achieved via the Pickering emulsion method. Subsequently, ultraviolet-assisted reduction and in situ polymerization of polypyrrole (PPy) are employed to construct a hierarchical 3D microcapsule. This robust architecture effectively improves leakage resistance, achieving a high encapsulation rate of 82.80% and exceptional cycling stability. The continuous 3D network formed by vacuum-filtered microcapsules increases the thermal conductivity to 0.435 W·m −1 ·K −1 and the electrical conductivity to 90.09 S/m. Meanwhile, the synergistic rGO/PPy network provides broadband optical absorption and high electrical conductivity, yielding photothermal and electrothermal conversion efficiencies of 91.25% and 78.86%, respectively. In practice, the composite reduces the peak temperature of a simulated CPU by 12.06 °C, and integration with a thermoelectric generator (TEG) enables simultaneous solar-thermal-electricity conversion. This work pioneers a scalable route for high-performance composite phase change materials in advanced thermal management and multi-source energy harvesting.