Evaporation Thresholds in Superthermal Solar Interfacial Evaporation: Urgency, Mechanism and Quantitative Prediction

High efficiency interfacial evaporation through photothermal conversion and hierarchical porous structures has been a promising approach to mitigate water scarcity. However, most studies only studied the performance under standard 1 kW/m² solar irradiation intensity, neglecting the critical evaporation efficiency degradation under superthermal conditions caused by unresolved evaporation thresholds that induce irreversible material damage. Thus, this work reveals that the urgency, qualitative mechanism, and quantitative predicted model to solve this problem. Firstly, experiments with nanoporous and microporous materials can all demonstrate that the evaporation thresholds phenomenon. Moreover, quantitative analysis confirms that the evaporation thresholds synchronize with water saturation dynamics for the mismatched interfacial heat and mass transfer, which can enable the surface water with high binding energy to dominate the evaporation process. Furthermore, we demonstrate the relationship between evaporation thresholds and pore structure indicated that 3D pore structure can provide a intermediate interfacial binding energy to delay the evaporation threshold. Therefore, we have developed a new fractal pore structure model for evaporation thresholds prediction, which can be validated by experimental data.