Contrasting Effects of Functionalization in Binary and Medium-Entropy MXene Coatings for Corrosion Protection
Developing scalable and environmentally benign anticorrosion coatings is critical for protecting steel infrastructure in chloride-rich environments. Here, a nacre-inspired multilayer epoxy coating reinforced with four MXene systems is investigated. This architecture forms a dense lamellar network that increases diffusion tortuosity and introduces electroactive surfaces for ion interactions. Electrochemical impedance spectroscopy (EIS) confirms that the multilayer design increases coating resistance from ~103 to ~108 Ohm/cm2. A clear performance hierarchy was observed: P-(TiVCrMo)C3 > O-Ti3C2Tx > O-(TiVCrMo)C3 > P-Ti3C2Tx. Density functional theory (DFT) calculations reveal that P-Ti3C2 strongly adsorbs O2, indicating higher surface reactivity, while oxygen termination stabilizes the surface by partially passivating Ti sites. In contrast, P-(TiVCrMo)C3 exhibits strong adsorption of oxygen-containing species due to its multi-metal electronic structure, promoting the formation of protective oxides. These results highlight the delicate balance of surface chemistry, electronic structure, and compositional entropy in designing next-generation MXene-based anticorrosion coatings for marine and industrial environments.