An optimized double-layer MXene/chitosan interfacial solar evaporator with reduced water evaporation enthalpy via channel size minimization

Utilizing interfacial solar evaporator (ISE) to produce freshwater represents an effective solution to mitigate water scarcity. A key design strategy for improving evaporation efficiency in ISEs involves reducing the evaporation enthalpy of water. Herein, we prepared evaporation layers with varying channel sizes by controlling the cooling temperature, using chitosan and MXene as raw materials crosslinked with glutaraldehyde. These evaporation layers were combined with a chitosan monolith (CM) featuring a honeycomb-like porous structure as the water transport layer, resulting in the successful fabrication of a innovative double-layered interfacial solar evaporator (DISE) which possesses splendid thermal localization ability. The integration of the bilayer structure in DISE enables the evaporation layer to minimize water evaporation enthalpy, while maximizing evaporation efficiency and enhancing salt rejection. Among the samples, DMCML*-1 exhibited superior performance, attaining an evaporation rate of 3.01 kg m −2  h −1 under 1 kW m −2 simulated sunlight. It manifested excellent capabilities for seawater purification and wastewater recycling, maintaining stable evaporation rates over extended operational periods. This research not only provides an innovative method for the development of environmental, cost-effective, and high-efficiency ISEs but also addresses the challenge of balancing reduced evaporation enthalpy with enhanced water transport capacity, offering valuable insights for advancing the field.