Effect of Facet on Oxygen Vacancy Properties in δ-MnO₂ for Stable and Efficient Catalytic Ozone Decomposition

Manganese oxides (MnOx) serve as a classical catalytic material for ozone (O3) decomposition, while the accumulation of the peroxide intermediate (*O2) and water (H2O) significantly degrades its performance. In this study, the exposed (111) facet of δ-MnO2 was prepared to modulate the properties and content of oxygen vacancies (Vo). Experimental and theoretical results indicate that δ-MnO2 with the (111) facet possessed a lower Vo content compared to the thermodynamically stable (001) facet. Remarkably, despite the deficiency in Vo content, the rapid *O2 desorption enables the catalyst to achieve superior performance, along with excellent stability. Additionally, the dynamic adsorption and reaction of H2O with O3 significantly enhance the stability and water tolerance of the catalyst. The preferred Mn-0.2 maintained 95% O3 conversion after 24 h of reaction under harsh conditions (WHSV = 900 L·g–1·h–1 and 35% RH). This work provides and validates new insights into strategies for mitigating the rate-determining step in an environmental catalytic reaction.