Controllable fabrication of ZnO nanorods@cellulose membrane with self-cleaning and passive radiative cooling properties for building energy-saving applications

The energy consumption for building cooling occupies non-ignorable part of global energy consumption, causing the increasing aggravation of energy crisis and environmental deterioration. Because of the zero consumption and discharge features, researchers have attached much importance to the passive radiative cooling which is considered as a promising method with practical application potential. In this work, a superhydrophobic ZnO nanorods@cellulose membrane for efficient building radiative cooling was fabricated via in-situ growth method and followed by a modification process with sodium laurate. The obtained cellulose membrane exhibited high visible reflectance up to 93.6% and thermal emissivity of 0.841 in atmosphere window spectrum. An average 5 °C temperature reduction under direct radiation was obtained in simulation experiment owing to its good optical performance. Moreover, a water contact angle over 150° and the rolling angle less than 7° indicated the super hydrophobicity and associated self-cleaning properties. The good flexibility derived from cellulose enables membranes to adhere well to complex shaped surfaces. Therefore, the hydrophobic and flexible ZnO nanorods@cellulose membrane with effective passive radiative cooling performance is promising for applications in residential building cooling or even vehicles, machines and facilities cooling and maintain.