Waste paper-spent coffee grounds synergistically derived carbonized cellulose aerogel for multifunctional phase change materials: Enhancing thermal energy storage, Joule/solar heating, and electromagnetic shielding

To tackle UAV on-board electronics’ key pain points—single functionality, excessive weight, and poor thermal-electromagnetic integration—a sustainable multifunctional composite phase change aerogel (C-PCA) was developed via a dual biomass synergy: waste paper (WP) builds a macro load-bearing framework, while spent coffee grounds (SCG)-derived cellulose nanofibers (CNF) enable nanoscale cross-linking to jointly enhance structural stability. The fabrication involves three concise steps: directional freezing-freeze-drying to form CNF/WP aerogel, carbonization (700 °C, N 2 atmosphere) to obtain a porous carbonized aerogel (C-aerogel), and vacuum impregnation of PEG-1000 to prepare C-PCA. The optimal C-aerogel (Sample S1, WP/CNF mass ratio = 8:2) withstands a 200 g load without deformation; C-PCA retains a melting enthalpy of 130.2 J g −1 (91.8% of pure PEG-1000), reduces supercooling by 1.4 °C, and shows no leakage after heating at 60 °C for 120 min. Its thermal conductivity (351.4 mW m −1  K −1 , 1.5 times that of pure PEG-1000) ensures efficient heat transfer, while it reaches the phase transition temperature in 121 s under 1600 mW cm −2 simulated solar irradiation and 85 °C in 540 s under 15 V (UAV-adapted voltage). In the X-band (8.2–12.4 GHz), C-PCA achieves 33.98 dB electromagnetic interference (EMI) shielding (absorption-dominated, meeting UAV standards) and excellent infrared camouflage (surface temperature 23.1 °C, close to ambient 22.6 °C). This work realizes high-value utilization of waste biomass, providing a low-cost, eco-friendly solution for UAV on-board electronic systems.