Stable O₃ Decomposition by Layered Double Hydroxides: The Pivotal Role of NiOOH Transformation

Because ozone (O₃) is a significant air pollutant, advanced O₃ elimination technologies, particularly those under high-humidity conditions, have become an essential research focus. In this study, a nickel-iron layered double hydroxide (NiFe-LDH) was modified via intercalation with octanoate to develop an effective hydrophobic catalyst (NiFe-OAa-LDH) for O₃ decomposition. The NiFe-OAa-LDH catalyst sustained its O₃ decomposition rate of >98% for 48 h under conditions of 90% relative humidity, 840 L/(g·h) space velocity, and 100 ppm inlet O₃ concentration. Moreover, it maintained a decomposition rate of 90% even when tested at a higher airflow rate of 2500 L/(g·h). Based on the changes induced by the Ni-O^II to Ni-O^III bonds in NiFe-OAa-LDH during O₃ treatment, catalytic O₃ decomposition was proposed to occur in two stages. The first stage involved the reaction between the hydroxyl groups and O₃, leading to the breakage of the O-H bonds, formation of NiOOH, and structural changes in the catalyst. This transformation resulted in the formation of abundant and stable hydrogen vacancies. According to density functional theory calculations, O₃ can be effectively decomposed at the hydrogen vacancies with a low energy barrier during the second stage. This study provides new insights into O₃ decomposition.