LAUSR

Abstract In this work, defect-enriched NiO film-coated nickel foam (NF@NiO) monolithic catalyst was prepared by an oxalic acid-assisting hydrothermal treatment without additional Ni sources and followed by a calcination treatment, which was then used as an ozonation monolithic catalyst for the first time. The formation mechanism and morphology control of NiO film, and the catalytic performance of NF@NiO were systematically investigated. It is found that the film was assembled by randomly NiO nanorods under the best conditions of 0.001 mol/L of H2C2O4, 7 mg/L of dissolved oxygen (DO), as well as the hydrothermal temperature of 120 ℃ for 18 h. Particularly, the coupling effect of H2C2O4 and DO on the morphology of NiO film and the properties of NF@NiO was revealed. Too low or too high DO would not result in a dense and complete NiO film and the absence of H2C2O4 only produced a film assembled by vertically-standing hexagonal NiO nanosheets with less vacancies (NiO nanosheets/NF). Due to the porous structure, rich defects of oxygen vacancies and undercoordinated Ni atoms, and the good redox ability, NF@NiO presented excellent catalytic performance for ozonation of toluene (about 95% of toluene removal efficiency for 350 min and 74.0% of mineralization efficiency, 7 times the breakthrough time of NiO nanosheets/NF). This work shed a light on the design and preparation of NiO monolithic catalysts for ozonation of VOCs.