Controllable Synthesis of ZnAl Layered Double Oxide for Passive Radiative Cooling

Passive radiative cooling (PRC) shows potential for energy savings, especially in the construction and transportation industries. However, it is prone to efficiency loss due to influences from the environment. To address this challenge, we constructed a ZnAl layered double oxide (ZnAl-LDO) substrate, which has optical selectivity, and modified it with a cross-linked surfactant of SiO₂/PFDTES, finally yielding an advanced ZnAl-LDO_M2 coating material with PRC performance and enhanced environmental durability. According to the tests, the solar reflectivity and thermal emissivity of the prepared ZnAl-LDO_M2 coating can reach 99% and 98%, respectively, after being calcined at 500 °C for 4 h. In addition, the contact and slide angles for water and oil on the coating can be improved to 160.2°/5.4° and 141°/12.9°, respectively, demonstrating the amphiphobicity of the product. In an outdoor test, the obtained coating can reduce the temperature by up to 12.6 °C. Furthermore, the simulation results show that 29.82% of cooling energy expenditure can be saved if the coating is applied to the surface of the building. Moreover, the coating exhibits environmental tolerance abilities, such as resistance to acid and alkali corrosions. These data indicate that the as-prepared ZnAl-LDO_M2 coating has promising prospects in the field of eco-friendly refrigeration.