Reviewing MnOx-based catalysts for decomposition of indoor ozone

Ozone is a highly reactive gas and one of important air pollutants for both indoor and outdoor environments. The Occupational Safety and Health Administration (OSHA) guideline for the ozone level limit at workplaces is 100 ppb for 8-hour exposure and the Health Canada guideline for the residential buildings is 20 ppb for 8 hour exposure. Therefore, applying an ozone removal technology in indoor environments is crucial when outdoor ozone concentration is high and/or where strong ozone emission sources exist. Activated carbon-based filters, thermal oxidation, catalytic oxidation, and photocatalytic oxidation are air treatment technologies that have been applied for ozone removal. Among these technologies, the catalytic oxidation approach showed better results, particularly manganese oxide (MnOx) based catalysts, which can decompose ozone to oxygen at room temperature. The low cost as well as high catalytic activity are among the advantages of MnOx-based catalysts. High specific surface area, high density of oxygen vacancy, high reducibility, low average oxidation state, and low relative humidity are beneficial for ozone decomposition over the catalyst. This review presents the importance of ozone removal from the indoor environments, its exposure issues, and the recent studies on MnOx-based catalyst for ozone decomposition.