α-MnO2 catalysts with efficient ozone-catalyzed decomposition under high humidity conditions

Abstract

Ground-level ozone pollution poses significant risks to both ecosystems and human health, necessitating the implementation of effective control strategies. This investigtion concentrated on a monolithic ozone degradation catalyst composed of powdered α-MnO2 , throughly examining its catalytic performance, moisture resistance, and stability. The monolithic catalyst demonstrated optimal catalytic activity, achieving an ozone conversion rate of 99% following calcination at 400°C for a duration of three hours. Comprehensive characterization of the catalyst’s properties at pH levels of 1, 4, and 7 revealed that residual acid ions negatively impacted catalytic activity. Notably, the catalyst at pH 7 exhibited more oxygen vacancies, which correlated with the reduction of sulfate ion residues and the increased availability of more active sites during the washing process. Under conditons of pH 7 and a space velocity of 900,000 h-1, the α-MnO2 catalyst achieved conversion rates of 100% and 95% for 18 ppm ozone within three hours under 90% relative humidity and dry conditions, respectively. Furthermore, the monolithic catalyst demonstrated remarkable moisture resistance, performing effectively in continuous alternating humidity cycle tests and maintaining high humidity. It sustained 90% ozone decomposition efficiency after three hours of testing in high humidity conditions. Additionally, the α-MnO2 monolithic catalyst showed excellent stability, with an ozone conversion rate exceeding 99% throughout a 50-hour testindg period. These results highlight the significant potential of the α-MnO2 monolithic catalyst for applications in ozone removal.