A leaf-like structured membrane for highly efficient and persistent radiative cooling†

Abstract

Passive daytime radiative cooling offers a promising approach to address energy, environmental, and safety issues caused by global warming. However, the contradiction between high radiative cooling performance and long-lasting ultraviolet (UV) durability is a primary limitation at the current stage. Here, inspired by the ability of epidermal cells and palisade cells on the leaf surface to protect internal leaf structures (such as chloroplasts and nuclei) under drought and high-temperature conditions, a double-layer passive radiative cooling (PRC) porous membrane, which consists of an upper protective layer densely packed with highly ultraviolet-reflective inorganic particles and a bottom cooling layer doped with a variety of optically characterized inorganic particles, was developed to overcome these challenges. This special leaf-like structure and the synergistic effect of the inorganic particles ensure that the PRC membrane has a high solar reflectivity of 99.3% and a high mid-infrared (MIR) emissivity of ∼95%. In addition, the membrane still maintains excellent optical and mechanical performance after ultraviolet radiation treatment with a total radiation dose of 7000 MJ m⁻². Therefore, the unique structural design and excellent comprehensive performance of the membrane can greatly promote the practical applications of the PRC technology.