Molecular insights into enhanced water evaporation from a hybrid nanostructured surface with hydrophilic and hydrophobic domains

Solar-driven interfacial evaporation has attracted considerable attention owing to its outstanding efficiency in thermal energy utilization and desalination. Nanostructured surface designs of interfacial evaporation materials can favor the water evaporation through water-mediated interactions. However, molecular-level understanding of water evaporation on hybrid nanostructured surfaces with hydrophilic and hydrophobic domains remains to be explored comprehensively. Herein, we performed molecular dynamics simulations of water evaporation from hybrid nanostructured surfaces composed of a hydrophilic substrate covered with hydrophobic nanopillars. The simulation results suggest that the hydrophobic nanopillars on the hydrophilic surface can effectively increase the water evaporation rate, and the rate can be increased by ∼ 28.3% at the surface converages 30% of hydrophobic nanopillars, as compared to that obtained with a flat hydrophilic surface. The energy barrier of water evaporation, density distribution of interfacial hydrogen bonds, and the arrangement of water molecules in confined nanochannels between the hydrophobic nanopillars were analyzed. The results of the velocity vector distribution of water molecules and their dipole orientations suggest that the orderly arrangement of water molecules not only mediates the potential barrier of water molecules but also improves heat conduction in confined water as well as interfacial heat conduction between interfacial water molecules and hybrid surfaces. Moreover, the relationship between the evaporation rate and the features of the hybrid surface, including surface coverage with hydrophobic nanopillars, liquid film thickness, and the hydrophilicity and hydrophobicity of the substrate and nanopillars, respectively were evaluated based on the Pearson correlation coefficient. This work provides key insights into the molecular-level mechanism of the interfacial evaporation of water and furnishes a facile and general strategy for designing surface structures for highly efficient water evaporation.