Fabrication of stable ZnO/Zn–Al/Al₂O₃ superhydrophobic material on aluminum substrate for high photocatalytic and antibacterial activity

A stable superhydrophobic ZnO/Zn–Al/Al₂O₃ surface (ZnSHS) was fabricated on Al substrate by etching in NaOH solution, immersion in the aqueous solution of Zn(NO₃)₂, and finally, thermal annealing treatment. Thus, theZnO/Zn–Al/Al₂O₃ SHS has shown the static water contact angle of 161 ± 1° and a dynamic sliding angle of 2°. The surface morphology, elemental composition, crystal structures, and chemical bonding of samples were investigated by using scanning electron microscopy equipped with energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The anti-corrosion potential of the coated (ZnSHS) and non-coated Al substrates was analyzed by using electrochemical impedance spectroscopy (EIS), and corrosion current density (I_corr) of ZnSHS decreased 3.97 times that of Al sheet. The antibacterial effect of ZnSHS was found almost 99.99% after 24 h. Photocatalytic activity of samples was evaluated by the degradation of methylene blue (M.B.) at 25 °C in a solution mixture of H₂O₂. M.B. was photodegraded up to 98.11% in the presence of ZnSHS with a rate constant of 4.997 × 10^–2 s⁻¹. The number of cycles of reusability of ZnSHS as photocatalysis was 12th. The present work offers a practical approach to fabricate superhydrophobic material on Al and its alloys for advanced engineering applications. The antibacterial effect was found up to 94.85%, even after the 19th cycle of continuously reusing the ZnSHS sample in the antibacterial experiments.