A Mussel-Inspired\nand Recyclable Coating with Integrated\nDaytime Radiative Cooling and Triboelectric Energy Harvesting for\nIntelligent and Sustainable Buildings

Carbon neutrality necessitates new technologies for renewable\nenergy\nutilization, active regulation of heat exchange, and material recycling\nto promote green and intelligent building development. Currently,\nthe integration of these functions and characteristics into a single\ncoating material presents a significant challenge. Here, we demonstrate\na novel triboelectric and radiative cooling coating with mussel-inspired\narchitectures, fabricated using cellulose nanofibers and Mica-TiO<sub>2</sub> as a functional mortar and brick, respectively. The abundant\npolar groups and specific surface area of cellulose nanofibers enable\na high accumulation of induced electrostatic charges, allowing the\ncoating to act as a tribolayer to generate triboelectric outputs.\nThe regularly layered arrangement of Mica-TiO<sub>2</sub> endows fire\nresistance to the coating, which exhibits self-extinguishing properties\nand maintains 45% of its original electrical output even after direct\nexposure to flame for 20 s. Additionally, the created multilayered\nstacking morphology, as well as intense group vibrations of Mica-TiO<sub>2</sub>, facilitates high reflectivity (<i>R</i><sub>solar</sub> = 0.9) and long-wave infrared emissivity (ϵLWIR = 0.94), achieving\na daytime subambient temperature drop of 5.3 °C. Notably, the\ncoating can be recycled easily while maintaining its triboelectric,\nradiative cooling, and fire-resistant properties. This work provides\nan innovative strategy for unifying triboelectric and radiative cooling\nfunctions, as well as recyclability, into a single coating material,\noffering new insights for future sustainable and energy-efficient\nbuildings.