Janus 3D graphene based evaporator with controllable wettability for highly efficient solar desalination

Interfacial solar desalination has been widely favored as a convenient technology to relieve the prominent lack of clean water. However, it remains urgent and challenging to develop materials that can simultaneously reduce heat loss and provide effective channels for water transport without salt accumulation. In this work, we developed a free-standing Janus 3D graphene based evaporator modified by a wettability-controllable UV-O3 treatment method. The upper hydrophilic layer of the Janus 3DG plays the role of continuous water supplement for evaporation, while the bottom hydrophobic layer could support material floating on the water surface to ensure effective light absorption and contribute to heat loss reduction. Taking advantage of the synergistic effect of the structure, Janus 3DG delivers a stable water evaporation rate of 1.71 kg m−2 h−1 under 1 kW m−2 illumination, a highly efficient conversion efficiency of 94.1 % and exhibits excellent salt-resistance in high concentration simulated seawater (10 wt%) without salt accumulation. The Janus 3DG had satisfactory availability for solar desalination and wastewater purification. Our study establishes and validates a simple method for fabricating an efficient solar-driven evaporator for desalination.