Ozone Decomposition Mechanism at Different Structural Oxygen Vacancies on Manganese Dioxide

Abstract

MnO2 is a promising catalyst for ozone decomposition, and oxygen vacancy has been regarded as the determinant factor for decomposition effectiveness. MnO2 with two different oxygen vacancies, that is, [Mn3+]-V0-[Mn3+] and [Mn3+]-V0, was synthesized and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The catalytic decomposition rate of [Mn3+]-V0-[Mn3+] was significantly greater than that of [Mn3+]-V0. MnO2 with [Mn3+]-V0-[Mn3+] showed the lowest average oxidation state of Mn and the fastest electron transfer capacity. A new pathway for ozone decomposition at [Mn3+]-V0-[Mn3+] was proposed accordingly. The reaction sequence involved (i) dissociative adsorption of ozone to form an oxygen molecule and an atomic O– at [Mn3+], (ii) reaction of O– further with another O3 molecule to form [Mn4+]-O-O-[Mn4+], and (iii) [Mn4+]-O-O-[Mn4+] decomposition to form a gas-phase oxygen molecule and [Mn3+]-V0-[Mn3+] for further ozone adsorption. This work revealed a new avenue for designing efficient catalysts for ozone elimination.