Development and application of photocatalytic coating for roadside NO_x mitigation in Hong Kong

A facile chemical method for the development of photocatalytic coating products was proposed based on practical application perspective for the Hong Kong roadside nitrogen oxides (NO_x) mitigation. TiO₂-based photocatalytic coating PC-C film with crystallized size of around 5–6 nm was synthesized with the peptization of H₂O₂. The PC-C coating possesses a super-hydrophilicity surface and is proven to have a NO_x degradation rate of 46.8% with an optimum pH level of 7. In addition, the PC-C coating presents a promising photocatalytic NO_x degradation compared with other commercially available coating products and P25 when applied on two building materials of Poly-methyl methacrylate (PMMA) and concrete surface. A weather resistance simulation and a 180-day on-site field trial were carried out the attenuation effects of photocatalytic coating applied in outdoor exposure. Based on epidemiological estimation and field investigation, hospital admissions for respiratory diseases (HARD) and mortality cases (MC) could be reduced with the application of PC-C coating along the street canyon. This work demonstrates the feasibility of air pollution control measures for the local roadside NO_x using photocatalytic technology, offering promising health benefits with environmental remediation.