Scalable and sustainable radiative cooling enabled by renewable poplar catkin-derived films

Abstract

Passive radiative cooling is a vital strategy for mitigating the greenhouse effect. However, the widespread use of synthetic plastics as the primary constituent raises environmental concerns of plastic waste. Addressing these challenges necessitates the development of radiative cooling materials based on natural and renewable resources. Herein, we utilize the abundant but underutilized poplar catkins, which are currently perceived as harmful, to fabricate a poplar catkin-derived (PC) film for radiative cooling. The PC film exhibits exceptional cooling performance, with a maximum cooling power of 75.3 W m−2 under an average sunlight intensity of 819 W m−2. Remarkably, the PC film achieves a sub-ambient temperature reduction of 6.2 °C during 9:00–13:00, within a similar solar radiation intensity. Additionally, the PC film possesses outstanding properties, including UV resistance, mold resistance, and renewability. Even after multiple regeneration cycles, the film experiences only marginal decreases of 0.9 % in sunlight reflectance and 1.4 % in infrared emissivity (8–13 μm). Furthermore, the resulting film demonstrates superior resistance to mildew compared to wood, highlighting its potential for long-term usability. This work not only addresses the environmental concerns associated with synthetic plastics but also harnesses the untapped potential of readily available natural resources to develop sustainable radiative cooling materials.