MXene-reduced graphene oxide sponge-based solar evaporators with integrated water-thermal management by anisotropic design

The main issue limiting the performance of the solar evaporators is that water-thermal management is difficult to coordinate. Herein, we achieve integrated water-thermal management by designing hierarchical MXene-reduced graphene oxide sponges with anisotropic thermal conductivity and axial-directional water conveyance channels. The reduced graphene oxide acts as the sponge framework and carbon source for in situ synthesis of MXenes on the surface. The axial-oriented framework supports the structure and provides fast water transmission channels to the air-water interface. Meanwhile, the MXene nanosheets are vertically aligned on the framework surface, making the radial thermal conductivity of the sponges much greater than the axial one, which suppresses heat loss in the axial direction. The material exhibits an evaporation rate of 2.35 kg m⁻² h⁻¹ under one sunlight and maintains 85 % energy efficiency under weak sunlight (0.5-sun). Furthermore, the sponge shows a long working life with 96 % evaporation rate retention after a 30-day-sustained operation.