Breaking the Selectivity Barrier: Reactive Oxygen Species Control in Photocatalytic Nitric Oxide Conversion

Abstract Semiconductor photocatalytic technology holds promise in efficiently reducing low concentrations of gaseous nitric oxide (NO). However, the suboptimal selectivity in NO removal, leading to the undesired production of NO₂ byproducts, poses a challenge. In this study, a defective CdS/Na₂Ti₃O₇ heterostructure is rationally designed with strong electronic interaction and intimate interface contact for promoting charge transfer kinetics. This design refines reactive oxygen species (ROS) generation, resulting in an impressive 81% NO elimination and 99.7% selectivity toward nitrates. Detailed mechanistic studies reveal an intriguing catalysis scenario in which reactant molecules are selectively adsorbed and activated at different sites. Anionic vacancies on the CdS/Na₂Ti₃O₇ surface render the activation of molecular O₂ to reactive superoxide radicals (O₂ ⁻) species. Furthermore, intrinsic surface basicity and O vacancy sites of the Na₂Ti₃O₇ cocatalyst facilitate the capture and activation of acidic nitrogen oxides (NO_x) molecules as nitrate species, contributing to enhanced catalytic activity and selectivity. As a result, anionic vacancies and basic sites over CdS/Na₂Ti₃O₇ heterostructure synergistically regulate the NO_x oxidation pathway, refining the products toward nitrate with remarkable selectivity. These insights guide the development of advanced photocatalytic systems for environmental remediation, highlighting the importance of managing ROS production for efficient pollutant removal.