Photocatalytic semi-flexible pavement for NO removal to alleviate urban automobile emissions pollution

The escalating urban air pollution caused by vehicular nitrogen oxides (NO_x) necessitates sustainable solutions. Solar-driven photocatalytic NO removal represents a green approach, yet challenges remain in developing cost-effective photocatalysts with high removal efficiency. This study through the Fe-TiO₂ combined with thermal polycondensation method with g-C₃N₄ build heterojunction generated Fe-TiO₂/g-C₃N₄ photocatalyst, in order to improve its NO catalytic efficiency. The optimized photocatalyst achieves a single-cycle NO removal rate of 52.3 %, demonstrating the 10.7 % improvement compared to pure TiO₂. Following five cycles, the decay rate is only 5.52 %, which is significantly lower than the 12.45 % of TiO₂, thus indicating superior long-term stability. Microscopic characterization shows that Fe can induce the generation of oxygen defects inside TiO₂ to promote the separation of photogenerated electron-hole pairs; and induce the formation of a built-in electric field to enhance the separation of photogenerated charges with the heterojunction formed by the construction of g-C₃N₄. Moreover, the designed photocatalytic semi-flexible pavement incorporating this photocatalyst exhibits 65.33 % NO removal efficiency per cycle, 10.95 % higher than traditional TiO₂ based systems, with a total decay rate of 1.71 % after five cycles. Additionally, the pavement demonstrates excellent mechanical properties, including fivefold higher rutting resistance than conventional asphalt pavements. This study provides a new sustainable pavement removal scheme for mitigating urban exhaust agglomeration pollution.