Huang Liao, Hu Yaoxin, Yao Xupei, Chesman Anthony S R, Wang Huanting, Sagoe-Crentsil Kwesi, Duan Wenhui
Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia.
Yellow River Laboratory, Zhengzhou University, Zhengzhou 450001, China.
ACS Appl Mater Interfaces. 2024 Oct 9;16(40):54401-54411. doi: 10.1021/acsami.4c09365. Epub 2024 Sep 6.
Energy-free passive daytime radiative cooling (PDRC) technology makes it an attractive solution to both the building energy crisis and global warming. Spectrally selective porous polymers have great potential for practical PDRC applications owing to their cooling performance and scalability. A fundamental understanding of the relationship between the cooling performance and pore properties is crucial for guiding future structural designs of high-performance PDRC materials. However, one of the key challenges is achieving uniform nanopores and tailorable pore morphologies in the PDRC coating films. Here we demonstrate a strategy to use advanced metal-organic framework (MOF) nanocrystals as a sacrificial template creating a nanoporous poly(vinylidene fluoride) (PVDF) coating film with uniform-sized nanopores for highly daytime passive radiative cooling. The experimental evidence indicates that nanopores around 400 nm in size, comparable to the wavelength within the ultraviolet and visible spectra, along with an appropriate porosity of 37%, contribute to excellent solar reflectance (94.9 ± 0.8%) and high long-wave infrared emission (92.8 ± 1.4%) in the resulting porous PVDF films. This leads to subambient cooling of ≈9.5 °C and a promising net cooling power of 137 W/m at midday under solar intensities of ∼1275 and ∼1320 W/m. The performance equals or exceeds that of state-of-the-art polymeric PDRC designs, and this general strategy of tailing nanostructures is expected to open a new avenue toward high-performance radiative cooling materials for PDRC applications.
无能源被动式日间辐射冷却（PDRC）技术使其成为解决建筑能源危机和全球变暖问题的极具吸引力的方案。光谱选择性多孔聚合物因其冷却性能和可扩展性在实际的PDRC应用中具有巨大潜力。深入了解冷却性能与孔隙特性之间的关系对于指导高性能PDRC材料的未来结构设计至关重要。然而，关键挑战之一是在PDRC涂膜中实现均匀的纳米孔和可定制的孔形态。在此，我们展示了一种策略，即使用先进的金属有机框架（MOF）纳米晶体作为牺牲模板，制备具有均匀尺寸纳米孔的纳米多孔聚偏二氟乙烯（PVDF）涂膜，用于高效的日间被动辐射冷却。实验证据表明，尺寸约为400 nm的纳米孔，与紫外和可见光谱内的波长相当，以及37%的适当孔隙率，有助于在所得多孔PVDF薄膜中实现优异的太阳反射率（94.9±0.8%）和高的长波红外发射率（92.8±1.4%）。这导致在中午太阳强度约为1275和1320 W/m²时，亚环境冷却约9.5°C，净冷却功率有望达到137 W/m²。该性能等于或超过了最先进的聚合物PDRC设计，并且这种调整纳米结构的通用策略有望为PDRC应用的高性能辐射冷却材料开辟一条新途径。
