Efficiency and durability of carbon dots grafted TiO2-based coatings applied on concrete under peeling and washing trials

Abstract

In engineering practice, the durability of photocatalytic coatings is a major concern. Here two types of unique visible light-responsive coatings are proposed and placed on the concrete surface, consisting of vinyl chloride/vinyl ester/ethylene copolymer (as a binder) and carbon-dots-grafted TiO2 (TiO2-CDs) but different in fabrication. The first type is mono-layer coating (MLC), which involves directly spraying the TiO2-CDs suspension containing the binder onto the concrete. The second type was called double-layer coating (DLC), which involves applying a binder layer to the concrete surface before spraying the TiO2-CDs layer. These show that adding binder improves the coatings' anchoring on both MLC and DLC concrete substrates, along with desirable resistance to peeling and washing, when compared to the TiO2-CDs coated concrete without the binder. The well distributed binder in the TiO2-CDs-based coating inevitably decreases the photocatalytic efficiency of the MLC concrete due to the binder's masking effect on the coated surface. However, the DLC concrete fully exploits the binder adhesion by inserting a polymer matrix layer and therefore maintains a strong resistance to peeling and washing without compromising its photocatalytic efficiency. The proposed DLC approach enables the fabrication of highly cost-effective and durable photocatalytic coatings applied to cementitious materials.