Electrodeposition synthesis of 3D-NiO1-δ flowers grown on Ni foam monolithic catalysts for efficient catalytic ozonation of VOCs

[Display omitted] •3D-NiO1-δ flowers were in-situ grown on Ni foam (NF).•3D-NiO1-δ/NF monolithic catalysts showed high catalytic performance for ozonation of toluene.•Catalytic mechanism was revealed by both experiments and DFT calculations. NiO monolithic catalysts were synthesized by electrodeposition without additional Ni sources for the first time. The formation mechanism and morphology control of NiO grown on nickel foam were investigated. Among the different samples, fully developed 3D-NiO1-δ flowers anchored on nickel foam (3D-NiO1-δ/NF) presented excellent catalytic performance for ozonation of toluene (100% removal efficiency within 450 min, 9 times the breakthrough time of NiO film/NFs) due to its high specific surface area, rich oxygen vacancies (OVs), good redox ability and abundant empty space enclosed by the petals. The in-situ DRIFTS, ESR and DFT calculation results demonstrate that the bridge of two Ni around the subsurface OVs is the most active site, and the roles of OVs are to promote the adsorption and decomposition of ozone into surface O, •O2−, and •OH by chain reactions. This work shed a light on the design and preparation of monolithic catalysts for ozonation of VOCs.