Solar-driven interfacial evaporation desalination performance of femtosecond-laser-processed pure aluminum surfaces: A thermal engineering case study

Solar-driven seawater desalination represents a highly efficient, eco-friendly, and sustainable technology for freshwater production. Femtosecond laser-textured aluminum surfaces combine solar light absorption and seawater wicking capability to achieve water purification via interfacial evaporation. However, their practical application is restricted by unsatisfactory evaporation efficiency and poor long-term stability of superhydrophilicity. Herein, superhydrophilic aluminum surfaces were fabricated via femtosecond laser processing with optimized parameters: laser energy dose of 8.0 mJ, repetition frequency of 150 kHz, scanning speed of 9.5 mm s −1 , hatch distance of 45.80 μm, and three scan cycles. The optimized sample yields a favorable evaporation rate of 1.23 kg∙m −2 h −1 . The underlying evaporation mechanism is systematically investigated via characterizations of surface morphology, optical absorption, wettability, wicking behavior, and hydrogen bond configuration. The optimized surface achieves an average broadband solar absorbance of over 90% and exhibits a high initial antigravity wicking rate of 12.05 mm s −1 , while retaining stable superhydrophilicity after 150-day sealed storage. Even after 35 days of continuous evaporation, its wicking capability remains adequate to sustain stable interfacial water evaporation. The laser-induced hierarchical micro-nanostructures substantially enlarge the effective liquid-air evaporation area, which is critical for enhancing the evaporation performance.