Effect of K+ ions on efficient room-temperature degradation of formaldehyde over MnO2 catalysts

delta-MnO2 was prepared via a facile in-situ redox reaction and used for catalytic oxidation of HCHO, a major indoor air pollutant. The washing treatment during catalyst preparation could impose great effect on content of K+ and catalytic activity. delta-MnO2 catalyst without washing treatment contains the highest content of K+ ion and exhibits the best catalytic activity among various delta-MnO2 samples. The HCHO removal efficiency keeps at 100% for first 600 min. The delta-MnO2 samples were characterized by advanced technologies including XRD, Raman, XPS, TPR, TPD and in-situ DRIFTS. The XPS results indicates that K+ ions increases the AOS value of Mn and the ratio of surface-adsorbed oxygen over delta-MnO2. The content of K+ ions improves the amount and redox ability of surface mobile oxygen species, enhancing catalytic oxidation of HCHO.