Carbon nanotubes@silicone solar evaporators with controllable salt-tolerance for efficient water evaporation in a closed system

Abstract

Solar interfacial evaporators are very promising for solving the clean water crisis, but suffer from serious salt-fouling. Moreover, solar evaporation performance declines significantly in closed systems (>30%), but the differences in salt-tolerance and evaporation performance between open and closed systems are unclear. Here, we report carbon nanotubes@silicone solar evaporators with controllable salt-tolerance for efficient water evaporation (1.34 kg m⁻² h⁻¹ under 1 sun) in the closed system. The evaporators have a superhydrophobic core and a superhydrophilic shell with precisely controllable thickness (T_{superhydrophilic}). Compared with the open system, the salt-tolerance of a specific evaporator in the closed system is much higher owing to lower light intensity, higher relative humidity and temperature. During long term continuous solar evaporation of seawater (10 h), the evaporation rate in the open and closed systems shows greatly different tendencies and even the same value with increasing T_{superhydrophilic}. This is because of changes in water supply, salt diffusion and heat loss with T_{superhydrophilic} and differences in the solar evaporation conditions (open or closed system). In addition, two strategies are used to enhance the water collection rate. This work sheds new light on the design of novel solar evaporators with high evaporation rate in closed systems.