Enhanced permeability and anti-wetting performance in solar-driven membrane distillation: Double-play of light-heat management and steric hindrance effect

Abstract

Solar-driven membrane distillation (SDMD) opens up promising opportunities to solve freshwater supply predicament in remote and off-grid locations. However, such technology suffers from low permeability and poor resistance to wetting, which impedes its extensive application. Herein, we provided a novel MXene-coating photothermal layer design protocol by inducing dual-spacing channels between their nanosheets through a hydrazine-induced way. For one thing, the hierarchical MXene layer structure possessed unique merits in light-heat management, including improved light adsorption, high light-heat conversion efficiency, and inert heat dispersion, which facilitated vapor generation. For another, the dual-spacing channels relieved the resistance for vapor transportation by the wide region, while the high surface hydrophobicity and narrow region of the channels performed as double barriers to prevent sault invasion to resist wetting. Based on the synergistic effect, a preeminent photothermal efficiency of 94% with a vapor permeance of 1.66 kg/m2h under 1 sun illumination for 3.5% salinity solution was achieved, which was 1.4 times higher than that of pure MXene membrane. Meanwhile, the MXene foam membrane could fulfill a stable freshwater intake of 10.6 L m−2⋅day−1 for a household under natural sunlight illumination using Huanghai seawater. This research provides a delicate one-stone-two-birds strategy in constructing high permeability and anti-wetting SDMD membrane for potable water production.