Photocatalytic efficiency of K-TiO₂ for air pollutant treatment: Synergistic effect of NO and acetaldehyde by K incorporation

Rutile TiO₂ samples with varying levels of K incorporation and annealing temperatures were tested as catalysts for NO oxidation under visible light. Among the catalysts, 0.374% K-TiO₂ annealed at 375 °C exhibited the highest NO removal efficiency. This superior performance can be ascribed to the reduced band gap and increased separation efficiency (or lifetimes) of electron-hole pairs by K. Conversely, its activity towards acetaldehyde oxidation was lower than that of bare TiO₂. Furthermore, the activity of 0.374% K-TiO₂ was investigated for simultaneous oxidation of NO and acetaldehyde, where the NO oxidation activity was not significantly influenced by acetaldehyde, whereas acetaldehyde oxidation activity was enhanced by NO. Our Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) studies suggest that K plays a crucial role in the mutual interaction between NO and acetaldehyde on the K-TiO₂ surface. Our findings suggest a significant role of mutual interaction between diverse pollutants on the K-TiO₂ surface for photocatalytic activity under real conditions.