Overcoming Raoult's Law via Ligand Field Polarization-Mediated Interfacial Water Activation for High-Performance Solar Evaporation.

Abstract

In traditional saline water evaporation systems, water evaporation is severely suppressed by salt solute, which strictly follows Raoult's law and thus hinders the solar-driven evaporation. Herein, a ligand field-induced electrostatic polarization strategy is proposed to thermodynamically activate water molecules through disrupting the ideal solution behavior restricted by Raoult's law. By co-coordinating Fe³⁺ and Co²⁺ within a sodium alginate hydrogel network, pronounced electron redistribution is induced in the polymer framework, generating a polarized coordination environment that disrupts the cooperative hydrogen-bond network of water and thereby decreases the water vaporization enthalpy significantly. Combined with a biomimetic hierarchical hydrogel featuring a bubble-channel and dual-network architecture, the embedded microcavities substantially expand the active evaporation interface, while the bimetal-regulated axial pumping and radial wetting dual-network enables efficient water transport and localized heat management. Therefore, the optimized hydrogel achieves a high apparent evaporation rate of 5.82 kg m^-2 h^-1 under 1-sun irradiation. Moreover, the atomically dispersed transition metal sites provide intrinsic catalytic activity for efficient degradation of organic pollutants. This work demonstrates an integrated strategy combining ligand field-driven thermodynamic water activation with multiscale dual-network engineering, offering a versatile platform for solar-driven desalination and wastewater purification in both remote and off-grid areas.