Engineered Dual Barriers: Fluorinated Graphite Lamellae–Aerogel Bilayer Coatings for Weather‐Resistant Superhydrophobic Thermal Shielding

ABSTRACT The deployment of thermal insulation coatings in outdoor construction is critically constrained by durability issues such as rapid aging, internal condensation, and rain erosion, which severely compromise service life and protective performance. To address these challenges, this study develops a hierarchically structured superhydrophobic bilayer coating with enhanced thermal insulation capability. The architecture comprises a bottom adhesive layer based on a carbon aerogel/fluorocarbon resin composite, which ensures strong substrate adhesion while providing abundant anchoring sites for functional particles, thereby reinforcing structural integrity. The top functional layer consists of densely packed fluorinated expanded graphite (F‐EG) flakes that retain the intrinsic lamellar graphite microstructure, generating a micro/nanoscale hierarchical surface topology. The carbon‐based components impart outstanding physicochemical stability, enabling the coating to withstand accelerated aging conditions, including 300 d immersion in aggressive salt, acid, and alkali solutions (pH 1–14), prolonged ultraviolet irradiation (3000 h at 500 W m − 2 ), and simulated torrential rain erosion (impact velocity of 5 m s −1 ). Notably, the coating preserves superhydrophobicity after 200 d of outdoor exposure with minimal surface fouling. The porous carbon aerogel matrix provides stable thermal insulation (thermal conductivity < 1.59 W m −1 K −1 ) even under 99% relative humidity, which is attributed to the moisture‐mitigating vapor‐barrier function of the F‐EG layer. Field trials on building rooftops demonstrate excellent thermal regulation, with significantly reduced indoor temperature fluctuations compared with monolithic aerogel coatings and commercial products. This dual‐barrier design establishes a promising strategy for durable, high‐performance thermal management in harsh outdoor environments.