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 (NOx) 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 NOx 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.