Scalable Hydrogel Evaporator Enabled by Ion–Regulated Water States for Solar Desalination

ABSTRACT Hydrogel–based evaporators have long been regarded as star materials in the field of photothermal interfacial evaporation owing to their remarkable performance. However, achieving the synergistic optimization of water–state regulation and structural stability remains a highly appealing yet challenging goal. In this work, a multifunctional photothermal evaporator was designed by incorporating MXene nanosheets and magnesium ions (Mg 2+ ) into a poly(vinyl alcohol) (PVA) hydrogel matrix, which was subsequently anchored onto a nonwoven fabric substrate. Density functional theory (DFT) calculations reveal that Mg 2+ forms stable hydrated coordination structures on MXene surfaces, achieving a favorable balance between water–binding strength and electronic coupling, thereby enabling effective water–state regulation and energy transfer. Finite element simulations further demonstrate that a 10° inclination of the evaporator relative to the water surface markedly enhances light harvesting and vapor diffusion. As a result, the as–prepared PFMs evaporator achieves an evaporation rate of 3.88 kg·m −2 ·h −1 under 1 sun, ranking among the high–performing hydrogel–based evaporators reported to date while exhibiting excellent long–term stability. Large–scale tests using a 100 cm device verify its good scalability. This work provides a feasible strategy for developing efficient, durable, and scalable solar evaporators.