Preparation of PDMS-modified epoxy composite coatings by Mn/Cl co-doping of g-C3N4 and their enhanced photocatalytic activity and aging resistance

Abstract

Recently, photocatalytic coatings have been widely used as an effective solution for removing pollutants from building facades, owing to their simplistic architecture, broad applicability, and cost-effectiveness. This study successfully develops manganese–chlorine-co-doped carbon nitride nanosheets through a one-step calcination approach, significantly enhancing their photocatalytic efficiency due to the synergistic benefits of dual-element doping. This process results in an increased specific surface area and the generation of novel energy states, effectively lowering the band gap. The optimized g-C₃N₄ demonstrates a remarkable degradation of 99% of the RhB solution within 60 minutes, with a degradation rate constant that is 5.6 times greater than that of standard g-C₃N₄. Furthermore, the synthesized carbon nitride nanosheets are blended with modified epoxy resin to create a multifunctional integrated coating, exhibiting superior photocatalytic and anti-aging attributes. The incorporation of the photocatalyst provides UV-shielding properties to the system, while the introduction of polydimethylsiloxane enhances the epoxy resin's characteristics. The resulting composites display stable properties (including microstructural integrity, gloss, and water contact angle), improve the hydrophobic nature of the epoxy resin (raising the contact angle from 72° to 125°) and mitigate its weathering degradation. Additionally, the photocatalysts endow the coatings with the capability to degrade surface contaminants photochemically; the cleaning efficacy of these coatings is assessed using RhB as a degradation model. This composite not only prolongs outdoor durability but also suggests avenues for enhancing the cleaning effectiveness of coatings.