Construction of Pd-Modified NiCoOx Hollow Nanospheres with Surface Hydroxyls and Oxygen Vacancies for Highly Enhanced Catalytic Toluene Oxidation Activity

The catalytic activity of well-designed hollow spinel NiCoOx catalysts synthesized using a facile hard template method was investigated. These materials demonstrated higher performance during toluene oxidation compared with NiO, Co3O4, and NiCoOx nanosheets with 100% conversion at 250 °C. Hollow NiCoOx nanospheres (h-NiCoOx) were found to have numerous surface hydroxyl groups and large surface areas together with oxygen vacancies, all of which promoted the oxidation reaction. Varying amounts of Pd were loaded on h-NiCoOx and the catalytic efficiency was further improved. A 2.0 wt % Pd/h-NiCoOx sample exhibited the highest activity, achieving approximately 100% toluene conversion at 190 °C with a lower activation energy of 41.9 kJ mol–1 compared with the pristine h-NiCoOx (95.6 kJ mol–1). These results demonstrate that such materials have potential applications in the mitigation of toluene pollution.