Surface Roughness Engineering for High-Salt-Tolerant Solar Evaporator with Enhanced Efficiency in Sustainable Desalination.

Abstract

The accumulation of dense crystal layers on solar evaporators compromises performances by reducing light absorption efficiency and obstructing water transport channels, ultimately diminishing evaporation rate. To mitigate this issue, spatially separated crystallization sites can be engineered on the evaporator surface to disrupt salt adhesion and prevent dense layers formation. In this study, we developed a 3D column-shaped wood evaporator (KAC-DW) by coating delignified wood (DW) with KOH-activated carbon (KAC). The KAC coating creates microstructured surface featuring abundant protrusions (~144 mm-2, each 20 μm in height), which effectively inhibit salt crystal adhesion. Under 1 kW m-2 solar radiation with a 15 wt% NaCl solution, the KAC-DW evaporator achieved an impressive water evaporation rate of 8.18 kg m-2 h-1 over 96 h (0 m s-1 wind speed)-more than double the performance of uncoated DW (3.91 kg m-2 h-1). This enhancement stems from two key mechanisms: (1) the KAC protrusions prevent dense crystal layer formation, preserving open surface channels for evaporation, and (2) they promote the growth of loose salt crystals, thereby expanding the effective evaporation area and further boosting the evaporation rate.