Achieving Efficient Solar Energy Harvesting and Storage through Phase‐Change Material with Copper–Carbon Dual Network

Solar energy is a widely used renewable energy source, but its efficient harvesting and rapid storage in phase‐change materials (PCMs) remain challenging. This study presents a dual continuous network strategy to simultaneously enhance photothermal conversion and thermal conductivity for improved solar thermal storage. Copper foam serves as the primary thermal network, while expanded graphite forms a secondary continuous network within the pore channels. The top portion of this dual network acts as an optical absorber, efficiently capturing solar energy, while the bottom ensures rapid and uniform heat transfer to the PCM. With only 24 wt% filler content, the thermal conductivity of the composite PCM increases from 0.2 to 5.3 W/m·K, achieving 94% ultraviolet–visible‐near infrared (UV–Vis–NIR) absorptivity. Meanwhile, the latent heat remains 176 J g⁻¹, surpassing similar materials in performance. These results highlight the potential of this composite PCM for advanced solar energy storage applications.