Biomimetically spider web-like hydrogels for high-efficiency solar evaporators

Abstract

With the increasing population, the shortage of freshwater resources has become a problem faced by human beings. Although many hydrogel solar evaporators achieved high evaporation rates by increasing the intermediate water content to reduce the enthalpy of water evaporation, it is still challenging to explore effective photothermal materials to construct efficient hydrogel solar evaporators. Here, inspired by the spider web structure, interconnected porous hydrogels were proposed by cross-linking heterojunctions and polymers. For the first time, MXene heterojunction is applied to solar evaporators. The introduction of SnS2 greatly improves the light absorption of MXene, at the same time, benefiting from the multi-scale macro/micro fiber network structure, MXene-SnS2 hydrogel (MSH) has a good “lock-in” performance, which makes the heat locally distributed near the evaporable water. As a result, the MSH evaporator has a low enthalpy of evaporation, with an evaporation rate of 3.3606 kg m−2 h−1 in 3.5 wt% salt water, and can maintain 1.9 kg m−2 h−1 even in 10.5 % brine. The evaporators present superior purification performance for seawater, could maintain high and stable evaporation performance for 72 h. This design principle and excellent performance provide a potential method and design concept for seawater desalination.