Superhydrophobic and Recyclable Cellulose-Fiber-Based Composites for High-Efficiency Passive Radiative Cooling

Abstract

Passive daytime radiative cooling (PDRC) involves cooling down an object by simultaneously reflecting sunlight and thermally radiating heat to the cold outer space through the Earth's atmospheric window. However, for practical applications, current PDRC materials are facing unprecedented challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination. Herein, we develop scalable cellulose-fiber-based composites with excellent self-cleaning and self-cooling capabilities, through air-spraying ethanolic poly-(tetrafluoroethylene) (PTFE) microparticle suspensions embedded partially within the microsized pores of the cellulose fiber to form a dual-layered structure with PTFE particles atop the paper. The formed superhydrophobic PTFE coating not only protects the cellulose-fiberbased paper from water wetting and dust contamination for real-life applications but also reinforces its solar reflectivity by sunlight backscattering. It results in a subambient cooling performance of 5 °C under a solar irradiance of 834 W/m 2 and a radiative cooling power of 104 W/m 2 under a solar intensity of 671 W/m 2 . The self-cleaning surface of composites maintains their good cooling performance for outdoor applications, and the recyclability of the composites extends their life span after one life cycle. Additionally, dyed cellulose-fiber-based paper can absorb appropriate visible wavelengths to display specific colors and effectively reflect nearinfrared lights to reduce solar heating, which synchronously achieves effective radiative cooling and esthetic varieties.

Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

“…The cooling wood achieved continuous subambient conditions during the day and night (Figure 4b). Similarly, other cellulose‐based materials [ 35,41–48 ] as efficient IR emitters have been explored for PDRC. Tian et al.…”

Sustainable and Inexpensive Polydimethylsiloxane Sponges for Daytime Radiative Cooling

“…Interestingly, our PDMS sponge shows a thermal conductivity of 0.06 W (m K) −1 , which is the lowest value among recently reported radiative cooling materials and is suitable for building envelope. [ 11 , 29 , 48 , 49 ]…”

The gorgeous transformation of paper: from cellulose paper to inorganic paper to 2D paper materials with multifunctional properties

“…In fact, paper consisting of cellulose fibers (20–50 μm in diameter), as a material with high solar reflectivity ( R solar ) of about 0.89 and an excellent infrared thermal emissivity ( ε IR ) of 0.92, is a good candidate for passive daytime radiative cooling (PDRC). 155 Tian et al 147 reported the preparation of superhydrophobic paper-based composites with self-cooling and self-cleaning properties by coating poly(tetrafluoroethylene) (PTFE) particles with extremely high reflectivity and extremely low surface energy via physical adsorption and mechanical interaction. The superhydrophobic coating endowed the paper with self-cleaning properties and could avoid the reduction of radiative cooling performances caused by contaminations such as floating dust, dirt, and soot on the surface of the paper (Fig.…”

“…The resultant self-cooling paper exhibited a subambient cooling performance of 5 °C under a solar irradiance of 834 W m −2 and a radiative cooling power of 104 W m −2 under a solar intensity of 671 W m −2 . 147 Moreover, the emergence of this radiative cooling paper not only can broaden the multifunctional applications of paper but also can pave the way for the development of energy-efficient and eco-friendly cooling systems.…”