Progress in TiO2-based photocatalytic pavements for urban NOₓ mitigation: A comprehensive review
Year: 2026
Type: article
Abstract: Titanium dioxide (TiO 2 ) based photocatalytic pavements are a promising technology for lowering nitrogen oxide (NO x ) concentrations close to traffic. This review synthesises laboratory and field evidence on TiO 2 -based pavements and maps the research landscape. Bibliometric analysis (2010-2025) shows that annual research output has risen steadily. China and the United States lead productivity, and 'NO x ', 'nano-TiO 2 ' and 'asphalt pavement' form the current keyword frontier, whereas 'visible light', 'heterojunction' and 'selectivity' are still emerging themes. TiO 2 incorporation methods, direct, indirect, and surface application, were scrutinized for their photocatalytic efficiency. Direct mixing dilutes and encapsulates the catalyst: at equal loading, asphalt matrices remove roughly 100 times less NO x than cement mortar. Carrier-based indirect routes and surface coatings restore activity, and surface-mounted TiO 2 aggregates achieve higher abatement with about seven times less TiO 2 , but coatings can lose most of their activity within 2-6 months under traffic. Humidity, flow rate, inlet concentration, temperature and irradiance govern performance, and cementitious substrates outperform bituminous ones. Credible field reductions cluster between 5 and 20% for roads and 10-25% for illuminated tunnels, with single-digit effects the norm under overcast, humid or soiled conditions. Durability rather than peak reactivity must therefore become the yardstick, and a four-metric readiness framework (FEP, MISB, EIRP, TELV) with measurable thresholds is proposed to enable standardised, whole-system evaluation.
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: hybrid
Funder: Universiteit Antwerpen
Award: G9000855931
OpenAlex ID: W7219055109