This study explores the development of an organic-inorganic hybrid coating to enhance the corrosion resistance and photocatalytic properties of AZ31 Mg alloy modified by plasma electrolytic oxidation (PEO). The PEO process typically generates a porous oxide layer, which can reduce corrosion protection by allowing corrosive agents to penetrate the substrate. To address this limitation, phenopyridine (PHEN) and 2-methylimidazole (2-IMD) were incorporated into the PEO surface to form a robust organic layer on the Mg alloy. Potassium hydroxide (KOH) was used to adjust the pH, improving the interaction and solubility between the organic molecules and the PEO coating. The hybrid coating exhibited unique twig-like surface structures that contributed to forming a multifunctional coating with high corrosion resistance and superior photocatalytic activity. The PEO-PHEN-2IMD sample on the Mg alloy demonstrated exceptional corrosion resistance, with the lowest corrosion current density (I_corr) of 1.92 × 10^-10 A/cm², a high corrosion potential (E_corr), and the highest top layer resistance (R_top) of 2.57 × 10⁶ Ω·cm², indicating excellent barrier properties. Additionally, the coating achieved complete (100%) degradation of methylene blue (MB) within 30 min under visible light. Density Functional Theory (DFT) calculations provide deeper insights into the bonding mechanisms and interaction stability between PHEN, 2-IMD, and the PEO layer on the Mg alloy and MB dye. These findings confirmed the enhanced performance of the hybrid coating in both corrosion resistance and photocatalytic applications.

Modulating metal-organic framework’s (MOF) crystallinity and size using a polymer, in conjunction with a high surface area of layered double hydroxide, yields an effective strategy for concurrently enhancing the electrochemical and photocatalytic performance. In this study, we present the development of an optimized nanocomposite, denoted as 0.5PVP/ZIF-67, developed on AZ31 magnesium alloy, serving as an efficient and durable multifunctional coating. This novel strategy aims to enhance the overall performance of the porous coating through the integration of microarc oxidation (MAO), ZnFe LDH backbone, and ZIF-67 formation facilitated by the addition of polyvinylpyrrolidone (PVP), resulting in a three-dimensional, highly efficient, and multifunctional material. The incorporation of 0.5 g of PVP proved to be effective in the size modulation of ZIF-67, which formed a corrosion-resistant top layer, improving the total polarization resistance (R_p = 8.20 × 10⁸). The dual functionality exhibited by this hybrid architecture positions it as a promising candidate for mitigating environmental pollution, degrading 97.93 % of Rhodamine B dye in 45 min. Moreover, the sample displayed exceptional degradation efficiency (96.17 %) after 5 cycles. This study illuminates the potential of nanocomposites as electrochemically stable and photocatalytically active materials, laying the foundation for the advancements of next-generation multifunctional frameworks.

The difficulty in achieving a balance between photocatalytic efficiency and chemical robustness has been a barrier to the broad use of MgO as a versatile material, mainly because of its restricted surface activity. To overcome this, a novel surface modification technique is proposed. It involves the integration of highly stable SnO₂ and WO₃ nanoparticles, which are known to enhance surface activity. This approach aims to achieve an optimal balance between efficiency and stability by finely tuning the structure-surface reactivity relationship. The technique utilizes a plasma electrolytic oxidation (PEO) method. In this method, both the AZ31 Mg alloy substrate and SnO₂/WO₃ precursors undergo simultaneous oxidation. This is induced by high-energy plasma generated through high voltage. The results demonstrate that this process yields a MgO layer with a homogeneous dispersion of SnO₂ and WO₃ nanoparticles, significantly enhancing its overall performance. Corrosion measurements demonstrated enhanced electrochemical stability against chloride ions. The dual incorporation resulted in a hybrid film exhibiting a corrosion current density value of 7.57 × 10⁻¹¹ A/cm² and a high outer layer resistance of 5.17 × 10⁷ Ω.cm². Additionally, the dual incorporation of SnO₂ and WO₃ nanoparticles enhances the photocatalytic activity of AZ31 Mg towards tetracycline degradation. This results in a photocatalytic efficiency of 89.54% within 2 h of exposure to visible light using the BA-W-Sn sample, which outperforms other samples. This integrated strategy enables the study to contribute significantly to expanding the practical applications of MgO-based materials. It does so by simultaneously enhancing their photocatalytic activity and chemical stability.