Wood-inspired anisotropic PU/chitosan/MXene aerogel used as an enhanced solar evaporator with superior salt-resistance

Solar desalination technology is an effective approach to produce clean water through evaporating seawater driven by solar energy. However, it remains a great challenge to develop a kind of solar evaporator with high salt-resistance, great stability and superior efficiency. Herein, inspired by wood structure, a polyurethane/chitosan/MXene aerogel with directional channel structure was originally designed as the solar evaporator for desalination by the freeze-casting method. The constructed unique anisotropic three-dimensional (3D) structure enabled the solar evaporator with efficient water transport network, which can effectively improve the salt-rejecting capability. Meanwhile, due to the combination of the full spectral absorption capacity of MXene and the unique directional channel structure, a satisfactory evaporation rate (1.81 kg.m−2 h−1) and high evaporation efficiency (85.07 %) under one-sun irradiation were achieved. Moreover, taking chitosan and waterborne polyurethane (PU) as matrix materials endowed the evaporator with favorable mechanical stability, which made the evaporator continuously achieving high evaporation rate for 12 h under one-sun irradiation and stably floating on the high- concentration salt water for over 14 days. In addition, the evaporator showed excellent salt resistance performance owing to its anisotropic directional channel structure. Also, a series of simulation and numerical modeling were carried out to assist in proving the mechanism of water transportation and desalination in the evaporator. Together, this work may provide a promising avenue for developing an efficient solar evaporator with superior salt blocking ability that could be potentially used for long-term clean water generation.