More than 3.6 billion people worldwide face water scarcity, and conventional desalination still depends on energy-intensive methods. Solar-driven interfacial evaporation (SDIE) offers a greener alternative, but most photothermal materials lose efficiency by heating excess water and suffer from fragile coatings that fail under pressure.
A research team at Nanchang University has overcome these challenges with a bionic design inspired by crocodile skin cracks and leaf vein networks. Using a multi-step impregnation process, they created a multifunctional cracked metal-phenolic network (MC-MPN) coating on a sponge substrate. The crack structure promotes ultra-thin water layers, enabling efficient "confinement capillarity" that concentrates heat at the evaporation surface, achieving a record evaporation rate of 3.2 kilograms per square meter per hour.
The coating's metal ions, such as Fe3+, provide strong photocatalytic activity, breaking down organic dyes and antibiotics while evaporating water. Uniquely, the crack network also acts as a stress buffer, maintaining coating integrity under repeated compression. Laboratory tests showed stable evaporation and purification performance after 1,000 compression cycles, solving the long-standing challenge of mechanical durability in confinement capillarity systems.
The team further developed an outdoor solar desalination device based on this coating. Tested with South China Sea water for seven days, the system maintained evaporation rates of 2.8-3.3 kg m-2 h-1 under natural sunlight and removed more than 99 percent of pollutants from saline dye wastewater, producing clear water well below WHO drinking standards for ion concentration.
By integrating efficiency, stability, and multifunctionality, this cracked-coating approach marks a breakthrough for solar desalination technology. It lays the foundation for robust, scalable devices that can both desalinate and remediate water, with strong potential for addressing global water shortages.
