One-step construction of P(AM-DMDAAC)/GO aerogel evaporator with Janus wettability for stable solar-driven desalination

[Display omitted] •A Janus aerogel was tailored by one-step hydrothermal-freeze casting method without further modification.•An evaporation rate of 3.65 kg m-2h−1 with a solar-to-vapor efficiency of 98.9 % is obtained.•The Janus aerogel demonstrates good salt tolerance and long-term stability.•The Janus aerogel has good performance on the purification of high salt wastewater. The interfacial solar evaporation, as a promising energy-efficient desalination technology, still urgently requires the development of efficiency and salt-resistance of the three-dimensional evaporators. Herein, Janus aerogels with macroporous air capsule structure were prepared by one-step hydrothermal self-assembly and freeze-drying treatment of dimethyldiallylammonium chloride acrylamide polymer-graphene colloidal solution, and then used for photothermal evaporation of high salt wastewater. The Janus P(AM-DMDAAC)/GO aerogels (PGA) exhibited asymmetric wettability and roughness at their upper and bottom surfaces, which are favorable for photothermal conversion at the hydrophobic interface and sufficient water supply at the hydrophilic interface. The evaporation rate of 3.65 kg m−2h−1 and the photothermal conversion efficiency of 98.9 % were obtained under 1.0 sun irradiation, which was attributed to the special three-dimensional structure of the Janus PGA. Benefited from the excellent water supply properties and the special air capsule framework, the as-obtained Janus PGA evaporator exhibited robust recyclability and durability in simulated seawater for 10 d without any salt crystallization. This study provides a simple strategy toward construct Janus aerogels with macroporous air capsule structure for solar evaporation and high-salinity wastewater treatment.