One-Pot Synthesis of Porous Silicon Sponge with Hydrophobic and Thermal Insulating Properties for Effective Passive Daytime Radiative Cooling

Abstract

Passive daytime radiative cooling (PDRC) materials are recognized for their ability to reduce temperature by highly reflecting sunlight and dissipating their own heat through the atmospheric transparent window into the cold outer space. However, their performance is often compromised by surface contamination and thermal input. In this study, a hydrophobic and thermal insulating porous silicon sponge was successfully synthesized through a one-pot hydrolysis condensation approach. During warm daytime, the sponge can maintain the temperature inside the model 5.7 °C lower than the ambient temperature, while at cold nights, the indoor temperature is 1.5 °C higher than the ambient temperature. Moreover, thanks to the self-cleaning ability conferred by the sponge’s hydrophobic surface, which enables water droplets to slide off and carry away dirt particles, thus the PDRC functionality maintains its longevity and effectiveness.