Super-Hydrophobic Nanostructured Silica Coating on Aluminum Substrate for Moist Air Condensation

In the present work, nanostructured functionalized silica is coated on an aluminum (Al) substrate by the spray pyrolysis method to create a stable and effective super-hydrophobic substrate for water harvesting via moist air. Substrate characterization reveals that (1) major diffraction peaks corresponding to crystoballite SiO2 (C-SiO2), quartz (Q-SiO2), Al2O3, and Al2SiO5 are to be found at SiO2/Al interface; (2) strong chemically bonded methyl functionalized silica is confirmed on the Al surface by Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectrometry (XPS) shows the presence of Al-O-Si bond at the interface; and (3) the equilibrium contact angle of the water droplet on the coated substrate is measured to be 156° ± 5° with a hysteresis of 10° ± 3°. The coating is found to be stable for more than 365 days in a humid atmosphere. Finally, moist air condensation experiments confirm substantial augmentation of condensate collected ranging from 188 ml/m2-h over an untreated aluminum substrate to 750 ml/m2-h over the coated substrate. Hence, it is concluded that nanostructured silica-coated Al substrate is highly effective for enhancing the condensation of water vapor from a moist air environment.