Efficient solar-driven interfacial evaporation and desalination using simple, salt-resistant, carbon nanotube-based Janus evaporators

Desalination technology is an effective solution for global freshwater crisis, but conventional methods usually consume fossil energy. Solar-driven interfacial evaporation desalination offers a promising solution to address freshwater scarcity and energy crisis, its key feature is the solar absorber is at interface between seawater and above air, where localized heating generates vapor. Nonetheless, there remains crucial challenges in designing evaporators that are simple to prepare, salt-resistant, stable, and highly efficient in evaporation. Janus evaporators in this study demonstrated superior performance compared to other carbon nanotube-based evaporators reported in current literature, particularly in terms of evaporation and salt resistance. In-laboratory experimental results showed the evaporation rate of deionized water was 2.49 kg·m-2·h-1 and the energy conversion efficiency was 91% under 1 kW·m-2. Furthermore, evaporators exhibited excellent salt resistance performance, with evaporation rates of 2.0 and 1.9 kg·m-2·h-1 in Bohai seawater and 3.5 wt% NaCl solution, respectively. Additionally, salt crystals formed during the evaporation with salinity higher than 15 wt% for continuous 12 hours could be self-cleaned in absence of light. In outdoor environments, a simple device based Janus evaporator also exhibited good desalination performance. Overall, this study indicates great potential of Janus evaporators for future sustainable energy applications in solar desalination.