Engineered titanium dioxide-based photocatalysts for NOₓ abatement: navigating design strategies and structure activity relationships for practical air purification

Abstract

Among various mitigation strategies for nitrogen oxides (NOx), photocatalytic DeNOx approaches have emerged as a promising solution, largely due to advancements in TiO 2 -based photocatalysts known for their excellent stability, efficiency, and environmental compatibility. This review presents a comprehensive examination of TiO 2 -based DeNOx systems, detailing the underlying reaction mechanisms and their practical applications. The discussion covers a wide spectrum of TiO 2 -based materials such as pristine TiO 2 , modified TiO 2 (through doping, sensitization, and hybridization), TiO 2 composites (integrating metals, metal oxides, carbon, MOFs, and COFs), and innovative architectures (such as S-scheme heterojunctions, core-shell structures, and Janus designs). Emphasis is placed on synthesis and surface-engineering approaches to improve their charge-carrier dynamics, light harvesting, and crystal facet reactivity. The performance evaluation of various DeNOx systems is also made in terms of key metrics (e.g., quantum efficiency, space-time yield, kinetic reaction rate, and NOx removal efficiency). This review uniquely integrates structural design with mechanistic insight, highlighting the path forward for tailoring TiO ₂ -based photocatalysts for next-generation DeNOx systems capable of operating under realistic atmospheric conditions.