A facile MXene/PPy modified asymmetry sponge solar absorber enabling efficient and high salt resistance evaporation

Solar-driven interfacial water evaporation is emerging as a promising sustainable strategy to collect fresh water and attracts extensive attention in academia. However, solar evaporator that can inhibit salt crystallization and capable of facile scalable preparation is indispensable yet remain challenging to achieve. In this study, a solar absorber based on an asymmetric melamine sponge with the synergistic of MXene nanosheets and polypyrrole was proposed by a simple dip-coating method. The integration of these individual components of solar absorber enables efficient solar-thermal conversion, stronger light absorption, oxidation resistance and long-term stability. More importantly, the asymmetric effect of the trapezoid-structure prompt directionally salt ion transmission from the wide leg to the narrow leg and achieve surprising salt resistance. As a result, the evaporation rate of the solar absorber can reach to be as high as 1.751 and 1.691 kg m−2 h−1 under high salinity of 7 and 10 wt% NaCl solution with 1 sun irradiation. Meanwhile, its evaporation rate changed little and retained at a constant value during the continuous operation even after 300 h irradiation in highly salty water. Such a solar absorber is confirmed as a facile, scalable, efficient, stable and salt-resistant evaporator for desalinating seawater under harsh conditions.