Ce–NiO catalyst for efficient catalytic decomposition of ozone in high humidity environments

Abstract

Water-induced deactivation poses a significant challenge for transition metal oxide catalysts in ozone decomposition. In this study, CeO₂ doped NiO catalysts with excellent water resistance were synthesized via a simple co-precipitation method. The Ce–NiO catalysts exhibited high initial ozone decomposition activity, but the conversion gradually decreased under dry conditions. In contrast, the presence of water significantly enhanced the stability of Ce–NiO. The optimized Ce–NiO (0.1) catalyst could maintain >98% conversion of 200 ppm ozone for 60 h at 30 °C, 90% RH (relative humidity) and a WHSV (weight hourly space velocity) of 1 200 000 mL g⁻¹ h⁻¹. Characterization revealed that CeO₂ doping generated additional defect sites, which increased the number of ozone reaction sites and reduced water desorption energy simultaneously. Furthermore, water was found to participate in ozone decomposition through an additional pathway: water dissociates on the catalyst surface to form hydroxyl groups, which react with ozone to regenerate water. This additional reaction pathway prevents the generation of intermediate oxygen species that could occupy active sites, thereby enhancing the catalyst's stability under high RH conditions. Consequently, the Ce–NiO catalysts exhibited exceptional water resistance and stability. This work provides guidance and new insights for designing stable and water resistant ozone decomposition catalysts.