Highly Efficient Solar Vapor Generator Enabled by a 3D Hierarchical Structure Constructed with Hydrophilic Carbon Felt for Desalination and Wastewater Treatment.

Solar vapor generation holds great potential for seawater desalination and wastewater treatment. Although various efficient solar absorbers have been developed to enhance the performance of solar vapor generators in recent years, their efficiency is still limited by unnecessary heat loss. In this article, a novel 3D hierarchical solar vapor generator (3DHG) was constructed with hydrophilic carbon felt. Different from interfacial solar vapor generators reported before, the porous and hydrophilic channels of 3DHG were exposed to the air directly, which probably resulted in a lower saturated vapor pressure of 3DHG. Therefore, this structure was beneficial for vapor escaping and led to lower average temperature of 3DHG than that of the surroundings at the same time owing to negligible convection loss and radiation loss of 3DHG. The highest evaporation rate (ER) of 1.56 kg m-2 h-1 and efficiency of 98.1% were obtained under 1 sun. In addition, 3DHG was also used for industry dyeing wastewater treatment and exhibited a minimum ER of 1.45 kg m-2 h-1 even after 7 days. This study presents a novel approach not only to design a solar vapor generator with high efficiency but also widens its potential application in seawater desalination and practical wastewater treatment.