Enhancing photocatalytic efficiency and interfacial bonding on cement-based surfaces by constructing CaO-TiO2 hybrid catalysts

The application of titanium dioxide (TiO2) coating in cement-based materials faces challenges regarding its durability. This study presented the concept of 'induced bonding' for enhancing coating adhesion. By modifying TiO2 with CaO, nucleation sites were constructed on its surface, inducing the growth of hydration products and connecting the catalytic materials to the substrate. As a result, a novel dual-effect CaO-TiO2 hybrid catalytic material with enhanced photocatalytic efficiency and interfacial bonding was successfully developed using a mechanochemical-thermochemical method. The CaO-TiO2 catalyst was coated onto cement surfaces, and the mechanisms of interface enhancement were revealed by micro-scratch and microstructural tests. The results indicated that the synthetic catalytic materials exhibited excellent NO photocatalytic degradation performance, particularly at an activation temperature of 300 degrees C; the optimized NO degradation efficiency hit around 40 % with a NOx comprehensive removal amount approximately twice that of conventional TiO2. Moreover, the minimal generation of NO2 demonstrated a strong photocatalytic selectivity. This exceptional photocatalytic performance can be attributed to the interaction between TiO2 and CaO, along with its derivatives such as CaTiO3 and CaCO3, which promoted the formation of active species (center dot OH, center dot O2- , h+), and increased the absorption efficiency in the visible light region. Furthermore, the wear resistance and interface critical load of CaOTiO2 coatings were more robust than reference coatings. The CaO-TiO2 catalyst promoted hydration to form widely distributed and interlocked fibrous C-S-H gel, bridging the catalyst particles and enhancing the adhesion of the coating with the cement substrate, thereby improving its interfacial bonding performance.