Nickel foam supported NiFe₂O₄-NiO hybrid: A novel 3D porous catalyst for efficient heterogeneous catalytic ozonation of azo dye and nitrobenzene

Although great efforts have been devoted to heterogeneous catalytic ozonation (HCO) in the past several decades, the lack of efficient, stable, easily separable and recyclable HCO catalysts remains a bottleneck for practical application. In this work, we develop a facile method to prepare the NiFe₂O₄-NiO nanohybrid catalyst, which is grown firmly and densely on the surface of 3D porous nickel foam (NF). The obtained NiFe₂O₄-NiO/NF hybrid catalyst exhibits high activity, good stability and excellent recyclability for the degradation of methyl orange (MO) and nitrobenzene (NB) via the HCO. We demonstrate by experiments that our NiFe₂O₄-NiO/NF catalyst significantly accelerates the decomposition of O₃, and greatly enhances the generation efficiency of hydroxyl radicals (^•OH) and superoxide radicals (O₂^•- or HO₂^•). Among all examined catalysts, NiFe₂O₄-NiO/NF possesses the largest number of Lewis acid sites, which are proved to be the active sites for the production of ^•OH and O₂^•-. We reveal that the synergetic effect of the NiFe₂O₄/NiO interface, the presence of Ni³⁺ during the HCO, and the 3D porous structure of the hybrid catalyst are the main reasons for the high performance for the HCO.