Self-cleaning PTFE nanofiber membrane for long-term passive daytime radiative cooling

Abstract

Passive daytime radiative cooling (PDRC) is an innovative, eco-friendly, and electricity-free cooling strategy that involves spontaneously cooling a surface by reflecting sunlight and radiating heat to cold outer space. Currently, many kinds of research focus on the effects of material design and structure construction on PDRC performance. However, the PDRC suffers a significant challenge of performance degradation arising from surface contamination and poor long-term outdoor durability. Herein, we developed a simple, efficient, and scalable strategy to prepare a superhydrophobic poly-(tetrafluoroethylene) (PTFE) nanofiber membrane (SNM-PTFE) with outstanding radiative cooling and self-cleaning performance for various practical applications. The SNM-PTFE has an average infrared emissivity of 95.8 % and reflects 95.4 % of solar irradiance. It brought about a sub-ambient cooling performance of ∼ 14.4 °C under direct sunlight. Moreover, it demonstrated excellent above-ambient cooling performance by reducing ∼ 9.5 °C under sunlight, which exhibited unprecedented heat dissipation and solar heat-shielding properties. The self-cleaning surface of SNM-PTFE maintained its good cooling performance after being exposed to outdoor conditions for a full month. SNM-PTFE showed great promise for PDRC, which can further extend the application for residential, industrial applications, and human thermal management.