A super-hygroscopic SA-MXene@LiCl composite membrane with fast ab/desorption kinetics for efficient sorption-based atmospheric water harvesting

Abstract

The daily water productivity of sorption-based atmospheric water harvesting (SAWH) materials is significantly limited by their low moisture sorption capacity and sluggish ab/desorption kinetics. Here, a thin, porous, mechanically stable and high LiCl-loading content super-hygroscopic SA-MXene@LiCl membrane (SM@LiCl) was fabricated via vacuum-assisted filtration and freeze-drying methods. The thin and porous characteristics of the cross-linked SA-MXene network significantly reduce moisture transport resistance, while the wrapped hygroscopic LiCl effectively enhances its moisture capture capacity. When applied to SAWH, this nanocomposite membrane demonstrates an impressive water uptake performance of 1.69 g g⁻¹ within 1 h at 45 % RH and releases over 65 % of absorbed water after only 0.5 h of sunlight irradiation (1 kW/m²). With its high moisture sorption capacity and rapid ab/desorption kinetics, it can operate for up to 16 cycles per day in indoor environment, resulting in a record daily water yield of 19.46 L kg⁻¹ at 45 % RH. The present study presents a straightforward approach for the development of high-quality sorbents with improved ab/desorption kinetics for SAWH.