Engineered titanium dioxide-based photocatalysts for NOxabatement: 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 TiO2-based photocatalysts aided by their excellent stability, efficiency, and environmental compatibility. This review presents a comprehensive examination of TiO2-based DeNOx systems by focusing particularly on the underlying reaction mechanisms and their practical applications. The discussion covers a wide spectrum of TiO2-based materials such as pristine TiO2, modified TiO2 (through doping, sensitization, and hybridization), TiO2 composites (integrating with metals, metal oxides, carbon, MOFs, and COFs), and innovative architectures (such as S-scheme heterojunctions, core–shell structures, and Janus designs). Emphasis is also 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 conducted in terms of key metrics (e.g., apparent quantum yield, kinetic reaction rate, and NOx removal efficiency). This review uniquely integrates structural design with mechanistic insight, highlighting the path forward for tailoring TiO2-based photocatalysts for next-generation DeNOx systems capable of operating under realistic atmospheric conditions.