Unraveling the impact of SO2 on electron transfer and oxygen vacancy over MnOx-CeO2 for ozone decomposition

Abstract

Mn-based catalysts for O3 decomposition (deO3) in industrial flue gas suffer from serious deactivation due to SO2, especially its impact on surface electron transfer and oxygen vacancy remains unclear. Herein, irreversible deactivation over MnOx-CeO2 in presence of SO2 and H2O was mainly attributed to the decrease of surface area, low-temperature reducibility and oxygen vacancies (Vo). SO2 was easily adsorbed on MnOx-CeO2 and further oxidized into SO42− under the aid of O3. Electron transfer from SO2 to Mn4+ and Ce4+ produced stable and inactive metal sulfates, which inhibited electron transfer in the redox cycles between Mn and O in O3 and between Mn and Ce. Moreover, metal sulfates occupied Vo, while Vo generation became difficult and its recovery from desorption of adsorbed oxygen intermediates was restricted, hence less O3 could be adsorbed and decomposed. Metal Ce protected active Mn species by reacting with SO2 preferentially. H2O generated active hydroxyl groups on Vo to react with O3 and hindered the contact of SO2 with Mn species, increasing deO3 activity under SO2 atmosphere. This study offers new insights into the poisoning mechanism of SO2 on electron transfer and oxygen vacancy in deO3 process, and sheds light on rational design of anti-SO2 deO3 catalysts.