Multiscale Investigation and Mechanistic Insights into TiO2@CoAl-LDH-Modified Asphalt for the Photocatalytic Degradation of NOx

Abstract For the eco-friendly asphalt pavements with NOx degradation performance, TiO2@CoAl-LDHs were prepared and applied as asphalt modifiers. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicated that TiO2 was uniformly loaded onto the surface of the CoAl-LDHs, and TiO2@CoAl-LDHs have been successfully synthesized. The integration of TiO2 and CoAl-LDHs reduced the energy barrier for electron–hole pair formation upon light irradiation, resulting in the stronger absorbance of TiO2@CoAl-LDHs in both ultraviolet and visible light ranges. After combining TiO2 with CoAl-LDHs, the photogenerated electron transfer and separation efficiency of TiO2@CoAl-LDHs were significantly enhanced, and the recombination of electron–hole pairs was concomitantly suppressed. Compared with TiO2 and CoAl-LDHs, TiO2@CoAl-LDH-modified asphalt exhibited stronger interaction with NOx. Meanwhile, NOx diffused more easily and had a larger penetration proportion in TiO2@CoAl-LDH-modified asphalt. All of these contributed to better NOx photocatalytic degradation capability of TiO2@CoAl-LDH-modified asphalt. This study promotes the development of eco-friendly asphalt pavements.