A novel visible-light-responsive polymer carbon nitride carbonized coating: NO_x degradation and bonding performance

This study reported the preparation of a visible-light-responsive polymer carbon nitride carbonized coating (VLPCNC) using γ-C₂S and photo-responsive polymer carbon nitride (PCN), primarily designed for air purification. The effects of varying PCN content on the photocatalytic properties, bonding strength, and erosion resistance of VLPCNC were investigated, with the mechanism analyzed through a series of microscopic techniques. Results demonstrated that VLPCNC with PCN displayed excellent photocatalytic efficiency under visible light. A rise in PCN content from 10 % to 50 % led to a substantial enhancement in the NO removal rate, increasing from 287.5 μmol·m⁻²·h⁻¹ (14.7 %) to 720.9 μmol·m⁻²·h⁻¹ (44.1 %). Incorporating 10 % of PCN could improve the bond strength of VLPCNC with concrete substrate. PCN could act as nucleation sites that enhance the carbonation of γ-C₂S, thus improving the bonding. However, a high PCN content significantly weakened the bond, as the dilution effect lowered the concentration of carbonation products in the binder. The NO removal performance of VLPCNC with 10 % PCN only reduced by 5.8 % after 1 d scouring treatment and the reduction increased when PCN content increased. All of the VLPCNC could remain good photocatalytic properties after 7 d scouring. The PCN particles were partially encapsulated by calcium carbonate crystals and adhered to their surface, enhancing the anti-scouring performance of VLPCNC. Notably, VLPCNC-10 exhibited a balance of exceptional photocatalytic properties, mechanical strength, and durability.