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

δ -MnO 2 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. δ -MnO 2 catalyst without washing treatment contains the highest content of K + ion and exhibits the best catalytic activity among various δ -MnO 2 samples. The HCHO removal efficiency keeps at 100% for first 600 min. The δ -MnO 2 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 δ -MnO 2 . The content of K + ions improves the amount and redox ability of surface mobile oxygen species, enhancing catalytic oxidation of HCHO.