Salt-resistant MXene-charge gradient hydrogel evaporator with boosted water transport for efficient photothermal desalination

Solar interfacial evaporation represents a highly promising approach for generating potable water from seawater utilizing clean, abundant, and sustainable solar energy. MXene-based materials exhibit outstanding photothermal conversion in desalination applications but face challenges in water transport and salt removal. Here, we introduce an effective MXene-charge gradient hydrogel (MCGH) evaporator that leverages the Donnan effect for salt rejection and internal osmotic pressure for water conveyance. The MCGH evaporator achieved 3.1 kg m−2 h−1 evaporation rate in 3.5 wt% NaCl under 1 sun irradiation. It also operates effectively in concentrated brines, reaching a notable 2.1 kg m−2 h−1 evaporation rate in 20 wt% NaCl solutions. This work introduces a new approach for salt-tolerant MXene photothermal evaporators, holding great promise for sustainable solar desalination applications. [Display omitted] •We introduce an efficient vXene-charge gradient hydrogel (MCGH) evaporator using the Donnan effect for salt rejection.•2D MXene films harvest sunlight effectively, converting light energy into heat for water evaporation in desalination.•This solar steam generator uses an ion pumping effect and gradient porous structure for high osmotic pressure and salt barrier.