Hydroxyl Groups Cooperating with Oxygen Vacancies on NiO for Incredible Catalytic Ozone Decomposition

Ubiquitous ozone (O₃) pollution in the atmosphere and indoors is severely detrimental to human health and ecosystems. Catalytic decomposition into O₂ is widely considered to be a promising technology for O₃ pollution elimination in the ambient environment. Unfortunately, developing a catalyst with high activity and moisture resistance, as well as applications through a facile approach, remains a huge challenge. In this study, we synthesized an excellent, active, and stable NiO catalyst with double active sites of hydroxyl groups and oxygen vacancies for catalytic O₃ decomposition. The simple NiO catalyst exhibited nearly 100% conversion of 40 ppm of O₃ within 100 h at a space velocity (600 L g^-1 h^-1) and 50% RH, suggesting exceptional chemical stability and water resistance over a long time. The hydroxyl groups in NiO directly bonded with O₃, inducing the reconstruction of NiO to form a new intermediate reactive species (NiOOH) and facilitating the involvement of H₂O molecules in the reaction, thus inhibiting the negative effects of moisture. Meanwhile, the coexisting oxygen vacancies effectively regulated the local electronic structure near Ni to promote the release of intermediate species and increased the number of active sites, resulting in dramatically enhanced catalytic O₃ decomposition. The mechanisms of catalytic O₃ decomposition were elucidated, underlying the hydroxyl groups cooperating with oxygen vacancies, with the combined in situ DRIFTS, Raman, EXAFS, and density functional theory (DFT) calculations. This work not only demonstrates the great potential of NiO materials in catalytic applications but also deepens the insight into the mechanism of O₃ decomposition.