Multilayered CWO/MXene/PANI-Coated Thermoplastic Expanded Microsphere Sponge for Enhanced Solar Desalination Efficiency

Interfacial solar-driven evaporation (ISDE) is a promising method for addressing the global freshwater shortage. However, it remains challenging to develop an ISDE system that combines high evaporation rates, low cost, ease of processing, and self-floatability. In this study, we present a flexible, porous sponge photothermal material based on three-dimensional thermoplastic expanded microspheres (TEMs). TEMs feature a unique hollow structure, which provides thermal insulation and minimizes heat loss. Flexible porous sponges were selected as the water transport medium in the evaporation zone, while CWO, MXene, and PANI were used as photothermal absorbing coatings on the TEMs. These three photothermal materials possess distinct absorption spectra, allowing for multilayered light absorption and enabling full-spectrum sunlight utilization. The resulting flexible multi-TEMs@PANI/MXene/CWO sponge exhibits excellent properties, including low thermal conductivity, high absorption, and efficient thermal conversion. The system achieved an evaporation rate of 2.07 kg·m^-2·h^-1 under primary light and a photothermal conversion efficiency of 89.7%. This work offers a controllable, environmentally friendly, and stable strategy to address the pressing issue of freshwater scarcity.