Efficiency and durability of g-C₃N₄-based coatings applied on mortar under peeling and washing trials

Durability of photocatalytic coatings is a major concern in engineering practice. Here, two types of novel visible light-responsive coatings, both consisting of vinyl chloride/vinyl ester/ethylene copolymer (as a binder) and graphitic carbon nitride (g-C₃N₄) but different in fabrication, are proposed and applied on the mortar surface. The first type is mono-layer coating (MC), where the g-C₃N₄ suspension containing the binder is directly sprayed on the mortar. The second type is double-layer coating (DC), where the binder layer is applied on mortar surface before spraying the g-C₃N₄ layer. Results show that the binder addition leads to a good anchorage of the coatings on both MC and DC mortar substrates, along with desirable resistance to peeling and washing, compared to the g-C₃N₄ coated mortar without the binder. The well-distributed binder in g-C₃N₄-based coating inevitably decreases the photocatalytic efficiency of the MC mortar due to masking effect of the binder on the coating surface. The DC mortar, on the contrary, takes full advantage of the binder adhesion by inserting a binder layer and therefore holds strong resistance to peeling and washing without compromising its photocatalytic efficiency. The proposed DC technique provides a promising strategy to fabricate highly cost-effective and durable photocatalytic coatings applied on cementitious materials.