Interfacial solar vapor generation

With the development of human society and economy, the problem of energy shortage has become increasingly prominent. Because traditional fossil energy reserves are limited, non-renewable and cause environmental pollution in the process of utilization, the use of clean energy is considered to be the only way for human development. As a clean and sustainable energy source, solar energy has always been valued. The traditional bulk heating, due to the lower conversion efficiency (30%–50%) caused by optical and thermal loss, limits the further development and promotion of the technology. In recent years, the concept of interface solar vapor conversion has been proposed. The interface solar vapor conversion which means that with the micro-nanostructure design and effective optical and thermal control, sunlight is fully absorbed and its energy is transmitted to the water molecules only at the interface between water and air, so that the liquid is continuously converted into vapor and the heat loss of high-temperature absorbers to large bodies of water and radiation loss to the air are reduced. Therefore, to achieve effective solar-vapor conversion, there are many requirements for the absorber: (1) the absorber materials need to be kept on the surface of the water; (2) the absorber needs to have sufficient solar absorption rate; (3) the absorbed energy needs to be effectively heated the water layer in contact with the absorber, thereby achieve the water to vapor conversion process quickly and efficiently. With the advancement of research, a series of new materials and new structures have been proposed, which effectively solve the problem of optical absorption loss and thermal loss of absorbers to insure the adequate water supply, resulting in a significant increase in conversion efficiency (>90%). In this review, we describe the mechanisms of interface solar vapor conversion, including light absorption, thermal management, and water supply, and demonstrate recent advances in energy conversion efficiency through a series of micro- and nano-structured material designs. Then we introduced some of the major applications currently based on interface solar vapor conversion, including seawater desalination, sewage treatment, etc. We demonstrate some typical research with excellent salt rejection for these applications. Finally, we look forward to the future development of the interface solar vapor conversion. We pointed out several problems that need to be solved to further improve the energy conversion efficiency. With the resolution of these problems, the photo-thermal conversion efficiency is expected to reach 100%, and the cost can be further reduced which indicates a huge application market and research prospects in this field.