Surface growth of novel MOFs on AZ31 Mg alloy coated via plasma electrolytic oxidation for enhanced corrosion protection and photocatalytic performance

Abstract

In the pursuit of multifunctional coatings, the controlled growth of materials on stationary platforms holds paramount importance for achieving superior corrosion protection and optimal photocatalytic performance. This study introduces a cutting-edge approach, intertwining bifunctional metal-organic frameworks (MOFs) seamlessly into defective MgO layers produced by the anodic oxidation of AZ31 alloy. Key metallic oxides of Zn, Sn, and V take center stage as metallic sources for MOF formation, complemented by the organic prowess of l-Tryptophan as an α-amino acid linker. Leveraging the electronic structure of metallic oxides reacting with tryptophan molecules, controlled morphologies with distinct characteristics are induced on the defective surface of the MgO layer, enabling the precise modulation of surface defects. The hybrid composite demonstrates an adaptive microstructure in diverse aqueous environments, offering dual functionality with electrochemical stability and visible light photocatalytic activity for crystal violet degradation. Among the samples, the SnOF complex exhibited remarkable electrochemical stability with a low corrosion current density of 7.50 × 10⁻¹⁰ A·cm⁻², along with a 94.56 % degradation efficiency after 90 min under visible light exposure. The VOF complex, under similar visible light conditions, demonstrated exceptional performance with a higher degradation efficiency of 97.79 % and excellent electrochemical stability characterized by a corrosion current density of 3.26 × 10⁻⁹ A·cm⁻². Additionally, Density Functional Theory (DFT) computations shed light on the basic bonding patterns between MOFs and inorganic components, providing electronic understanding of their electrochemical and photocatalytic activities.