2D Nb₂C MXene-enhanced hierarchical hydrogel for efficient solar-driven water evaporation

Solar-driven interfacial evaporation has emerged as a sustainable solution to address global freshwater scarcity by converting solar energy into thermal energy for efficient water purification. To achieve rapid and energy-efficient steam generation, the development of advanced photothermal materials with optimized light absorption and water activation remains critical. Here, we present a three-dimensional polyvinyl alcohol/chitosan/Nb₂C MXene (PCN) hydrogel engineered for high-performance solar evaporation. The composite integrates Nb₂C MXene nanosheets into a hydrophilic polymer matrix through hydrogen bonding and electrostatic interactions, forming interconnected microchannels that enable broadband solar absorption (93% across 300-2500 nm) via MXene's plasmonic effects and light-trapping architecture. The synergistic combination of rapid water transport and weakened hydrogen bonding within the hydrated network significantly reduces the evaporation enthalpy to 1426 J g^-1. This design achieves an exceptional evaporation rate of 2.72 kg m^-2 h^-1 and a solar-to-vapor conversion efficiency of 93.2% under 1 sun irradiation, surpassing conventional hydrophilic polymer-based systems. The hydrogel's hierarchical porous structure facilitates effective thermal localization and sustains stable evaporation across varying solar intensities (1-5 sun), demonstrating adaptability for scalable applications. This work provides a rational strategy to design MXene-enhanced hydrogels for practical solar desalination and wastewater purification technologies.