Triple-Scale Structure-Induced Efficient Passive Radiative Cooling Combining Robust Anticondensation
Zehong Zhao, Chengning Tang, Enming Cui, Ningning Sun, Jianing Zhou, Jiancheng Lv, Lei Zhao, Yahua Liu, Shile Feng
Abstract
Passive radiative cooling holds promise for achieving subambient cooling without consuming energy, facilitated by emitting thermal radiation into cosmic space. However, previous approaches, focusing heavily on aligning structural scales with optical properties, have struggled with effective anticondensation, thus limiting their applicability in high-humidity or supercooled conditions. Here, we demonstrate a design that enables efficient passive radiative cooling while maintaining robust anticondensation performance, underpinned by a triple-scale structure comprising microscale polymer particles, submicrometer-scale interparticle gaps, and nanoscale pores on the particle surfaces. This design achieves an efficient sunlight reflectance of 0.98 and high mid-infrared emissivity of 0.91 driven by the triple-scale structure-enhanced Mie scattering and chemical bond vibrations in polymer materials, respectively, enabling a 10.9 °C subambient cooling under direct sunlight at ∼40% relative humidity. Notably, even at a high relative humidity of ∼70%, our design still manifests an average cooling of ∼4 °C compared to ambient temperature, quite exceeding that of traditional radiative cooling materials. This is attributed to the robust anticondensation performance characterized by a maximum droplet shedding radius of ∼47.6 μm and a condensation droplet coverage of ∼32.4%, attributed to the triple-scale structure-induced larger Laplace pressure force and smaller adhesion. Moreover, our design demonstrates robust durability, encompassing self-cleaning performance via condensing droplets, thermal stability below 500 °C, and antiultraviolet radiation above 100 h, which exhibits potential applications in thermal management in various extreme scenarios.