Co‐anchored Hollow Carbonized Kapok Fiber Encapsulated Phase Change Materials for Upgrading Photothermal Utilization

Abstract The efficient capture, conversion, and storage of solar energy present significant promise for advancing green energy utilization. However, pristine phase change materials (PCMs) are inherently inadequate for optical capture and absorption. To improve photothermal conversion properties, PCMs and metal‐organic frameworks derived Co nanoparticle‐anchored carbonized hollow fiber are advantageously integrated. The robust hollow carbon fiber tubular structure promises efficient thermal energy storage, fast phonon transfer, and excellent durability and structural stability after long heating‐cooling cycles. Plasmonic Co nanoparticles and broadband‐absorbing high graphitized hollow carbon fiber synergistically enhance light harvesting and energy conversion in composite PCMs, achieving 94.38% photothermal conversion efficiency (100 mW cm −2 ). This integration enables the simultaneous generation of electrical and thermal energy under randomly incident solar radiation. Attractively, the designed photothermoelectric system steadily realizes a continuous output voltage of 309.8 mV and output current of 70.0 mA (100 mW cm −2 ). This advantageous integrated design strategy provides constructive insights for developing next‐generation composite PCMs toward efficient photothermoelectric conversion and storage systems.