Superoxide Radicals Inducing Perturbation in Water Hydrogen Bond Networks for Enhanced Solar-Driven Water Evaporation

Abstract

Solar-driven interfacial evaporation (SIE) utilizes solar energy at the air/liquid interface, offering an energy-efficient alternative to conventional evaporation methods. Due to the strong hydrogen bonding between water molecules, water evaporation requires breaking these intermolecular hydrogen-bond networks, which demand a large amount of energy. As a result, achieving efficient evaporation remains a technological challenge. This study presents a novel approach that uses superoxide radicals (·O₂⁻) to disrupt the hydrogen-bond network and enhance evaporation rates. A composite heterostructure of reduced graphene oxide (rGO) and oxygen vacancy (Ov)-doped gadolinium oxide (rGO@Ov-Gd₂O₃) is developed to explore this mechanism. Gd₂O₃ with oxygen vacancies generates ·O₂⁻ under light irradiation. Compared to the rGO framework, the water evaporation rate of rGO@Ov-Gd₂O₃ is enhanced by 60%, reaching 4.03 kg/(m²·h). Molecular dynamics (MD) simulations and density functional theory (DFT) calculations confirm that this enhancement results from the disruption and weakening of the hydrogen-bond network by ·O₂⁻. This work highlights the potential of ·O₂⁻ to improve evaporation efficiency and demonstrates their broader applicability in organic dye degradation and brine purification, showcasing their value in solar-driven photothermal systems.