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 (NO_x), photocatalytic DeNO_x 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 DeNO_x 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 DeNO_x systems is also conducted in terms of key metrics (e.g., apparent quantum yield, kinetic reaction rate, and NO_x removal efficiency). This review uniquely integrates structural design with mechanistic insight, highlighting the path forward for tailoring TiO₂-based photocatalysts for next-generation DeNO_x systems capable of operating under realistic atmospheric conditions.