Evaluation of CO Oxidation over Co3O4-supported NiO Catalysts

The process of doping NiO onto Co3O4 for achieving resistance to sintering and obtaining long-term stability of catalytic activity was examined herein. A sample of cobalt oxide (Co3O4) was prepared from Co(NO3)(2)center dot 6H(2)O via precipitation by NaOH, and then calcined at 300 and 500 degrees C. The Co3O4-supported NiO catalysts were prepared by deposited precipitation of Ni(NO3)(2)center dot 6H(2)O with NaOH added in a dropwise manner into the suspended Co3O4 solution with various loading of nickel. Then, oxidation with NaOCl was employed to obtain NiO/Co3O4 catalysts (weight loading of Ni: 0.1 similar to 5 wt%). All of the samples were characterized by using XRD, SEM/TEM, BET, TPR and TGA techniques. Catalytic activities related to CO oxidation were tested from 0 to 200 degrees C in a self-designed fluidized micro-reactor. The results showed that the calcination temperature and loading of nickel were important parameters in the preparation process. With the lower calcined temperature and loading of nickel below 1 wt%, all the samples showed high initial catalytic activity for CO oxidation near room temperature. The synergistic effect can induce CO oxidation between NiO and Co3O4, and probably constitute a more suitable redox property for the 0.2% Ni/Co3O4 (C3) catalyst. Furthermore, only a slight decrease of CO conversion (less than 5%) was observed after 50 h of continuous reaction under 125 degrees C on this catalyst. The CO conversion could still remain above 75% after 50 h, which demonstrates that the 0.2% Ni/Co3O4 (C3) sample can function as a durable CO oxidation catalyst. We confirmed that our designed catalysts, based on tiny NiO nanoparticles, can be used as a component of a toxic gas abatement system.