Sol-gel synthesis of mesoporous NiO/ZnO heterostructure nanocomposite for photocatalytic and anticorrosive applications in aqueous media

Nanocomposites (NCs) of p-type NiO/n-type ZnO heterojunction with varied NiO content (0-10) wt% were produced by spreading NiO nanoparticles (NPs) on the ZnO (NPs) surface by sol-gel technique with Triton X-100 as a structuring & templating agent. The crystalline phase, structure, characterization, and surface morphology of the gel powde0r of the produced NiO/ZnO nanocomposites were investigated using different spectroscopic techniques such as FTIR, XRD, FESEM, EDX, HRTEM, BET and UV-Vis DRS. The photocatalytic performance of the produced NiO/ZnO nanocomposites was estimated by continuously degrading the methylene blue dye (MB) as an organic contaminant in aqueous media. The effects of several factors, such as dopant concentration, pH, photocatalytic dose, point of zero charge (PZC), and chemical oxygen demand (COD) were assessed and discussed. When pure ZnO (NPs) is compared to NiO/ZnO (NCs), both exhibit superior photocatalytic activity under UV and sunlight irradiation. The corrosion resistance of the NiO/ZnO (NCs) gel coatings was assessed via potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The photodegradation data shown that the NiO/ZnO (5 wt%) semiconductor is the best photocatalyst for methylene blue dye (MB) degradation among the manufactured semiconductors. Furthermore, when compared to alternative gel coatings and the untreated surface at various doping doses, the gel coating based on NiO/ZnO (NCs) with a concertation of (5 wt%) displayed the highest activity as a coating system for aluminum electrode. In addition, increasing the layer thickness of NiO/ZnO (NCs) gel films and co-dopant concentration in coating systems increase corrosion resistance. AFM micrographs revealed the creation of a protective multilayer of NiO/ZnO (NCs) coating films on the surface of aluminum. The experimental and spectral results confirmed that the synthesized novel mesoporous mixed NiO/ZnO (NCs) had potential photocatalytic and anticorrosive behaviors.