Insights into the simultaneous photocatalytic removal of low‐level <scp>HCHO</scp> and <scp> NO ₂ </scp> in the air by V‐doped titania nanotubes

Abstract NO 2 and HCHO are common pollutants in indoor air and are toxic gases that can cause significant health effects even at low concentrations. In an effort to simultaneously remove NO 2 and HCHO at low concentrations, this study used titania nanotubes (TNT) and modified TNT under UV irradiation to evaluate their photocatalytic performance over time. The V‐doped TNT catalyst showed better simultaneous removal efficiencies for NO 2 and HCHO, reaching 82.27% and 79.58%, respectively. The experimental results also showed that the HCHO concentration significantly affected the NO 2 removal efficiency. Combined surface characterization and photocatalytic experiments allowed us to propose a synergistic mechanism for the simultaneous removal of NO 2 and HCHO, involving the important roles of oxygen vacancies and photo‐activated lattice oxygen. The V 4+ /V 5+ pairs were identified as adsorption sites for NO 2 and as oxygen sources that help replenish oxygen vacancies. This mechanism helps explain the differences observed between individual and simultaneous treatments of NO 2 and HCHO.