LAUSR

In the study, the catalyst precursors of Ce-modified γ-MnO2 were washed with deionized water until the pH value of the supernatant was 1, 2, 4 and 7, and the obtained catalysts were named accordingly. Under space velocity of 300,000 hr-1, the ozone conversion over the pH = 7 catalyst under dry conditions and relative humidity of 65% over a period of 6 hr was 100% and 96%, respectively. However, the ozone decomposition activity of the pH = 2 and 4 catalysts distinctly decreased under relative humidity of 65% compared to that under dry conditions. Detailed physical and chemical characterization demonstrated that the residual sulfate ions on the pH = 2 and 4 catalysts decreased their hydrophobicity and then restrained humid ozone decomposition activity. The pH = 2 and 4 catalysts had inferior resistance to high space velocity under dry conditions, because the residual sulfate ion on their surface reduced their adsorption capacity for ozone molecules and increased their apparent activation energies, which was proved by temperature programmed desorption of O2 and kinetic experiments. Long-term activity testing, X-ray photoelectron spectroscopy and density functional theory calculations revealed that there were two kinds of oxygen vacancies on the manganese dioxide catalysts, one of which more easily adsorbed oxygen species and then became deactivated. This study revealed the detrimental effect of surface acid ions on the activity of catalysts under humid and dry atmospheres, and provided guidance for the development of highly efficient catalysts for ozone decomposition.