Photocatalytic degradation of vehicle emissions using reduced graphene oxide-titanium dioxide modified pavement materials in cold regions

To enhance the photocatalytic performance of titanium dioxide (TiO2) in degrading vehicle emissions on pavement surfaces, this study synthesized reduced graphene oxide-titanium dioxide (rGO-TiO2) composites with varied reduced graphene oxide (rGO) doping ratios via hydrothermal method. The microstructure and optical properties of the composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). Results showed that rGO incorporation significantly improved the visible-light utilization and photocatalytic efficiency of TiO2. Targeting cold-region applications, an rGO-TiO2 photocatalytic asphalt mixture and a dedicated vehicle emission degradation test system were developed, with the composite applied as a water-based coating on asphalt specimens. Degradation experiments revealed optimal performance at 5.0 wt% rGO doping and 667 g/m2 coating spray amount. Low-temperature environments notably reduced degradation efficiency for hydrocarbons (HC) and carbon monoxide (CO) but had minimal impact on nitrogen oxides (NO). This research demonstrates the potential of rGO-TiO2 modified materials for developing sustainable, eco-friendly pavements in cold regions.