A bio-inspired nanocomposite membrane with improved light-trapping and salt-rejecting performance for solar-driven interfacial evaporation applications

Solar-driven interfacial water evaporation is a rapid emerging technology to address the global water crisis. Efficient solar absorption as well as robust salt-rejecting performance are among the critical requirements of this technology. Here, we report a novel double-layered nanocomposite membrane with improved solar absorption capability while simultaneously achieving enhanced salt-rejecting performance for solar-driven interfacial evaporation applications, such as seawater purification. Two bio-inspired material engineering strategies are utilized: first, inspired by black butterfly wings, a top sublayer based on MXene nanostructures is utilized to reduce light reflection and thereby improve its photo-thermal efficiency. Secondly, inspired by the selective mass transport capability of plant root cells, a bottom sublayer based on reduced graphene oxide (rGO) nanosheets with similar characteristics is designed and fabricated. The narrowed interlayer spacing between adjacent rGO nanosheets is demonstrated to effectively transport water molecules while rejecting salt ions. Finally, the nanocomposite [email protected] membrane achieves an evaporation rate of 1.33 kg m−2 h−1 and efficiency of 85.2% at 1 Sun. And the efficiency maintains 81.4% after 40 cycles of testing in seawater. In addition, simulations are performed to understand the light-trapping phenomenon for the MXene nanostructured surface. This bio-inspired work provides valuable insights for designing next-generation solar absorbers.