Influence of water molecule on active sites of manganese oxide-based catalysts for ozone decomposition.

Developing an efficient approach to decompose ground-level O in humidity is crucial for preventing O pollution in practical application scenes. In this study, MnO, CuO, and Cu/MnO were synthesized to investigate the influence of HO on the variation of active sites during O decomposition. The structural characterizations of the as-synthetic catalysts were measured by N2 physisorption, XRD, SEM, O-TPD, H-TPR, TG, and FT-IR analyses. In dry conditions, the elimination rate of O followed the sequence of MnO > Cu/MnO > CuO. The introduction of Cu to MnO enhanced the surface area and pore volume of Cu/MnO, accordingly diminishing the amounts of surface defects and the participation of sub-surface lattice oxygen for catalytic cycle, indicating that surface defects and oxygen vacancies (V) determined the catalytic activity for O decomposition. In humid conditions, the elimination rate of O changed to the sequence of Cu/MnO > MnO > CuO, with a variation rate compared to dry conditions of -62.9% for MnO, 14.2% for CuO, and 27.7% for Cu/MnO. The decrease of participant sub-surface lattice oxygen and the accumulation of intermediates in humidity diminished the decomposition of O on MnO, while the active species such as superoxide radicals generating from the reaction of HO and Cu/MnO facilitated the participation of V and the desorption of O from the occupied active sites, accelerating the catalytic cycle on Cu/MnO. This work developed a deeper understanding of the influence of HO on catalytic activity, promoting the performance of MnO-based catalysts for practical O decomposition.