Various surface area (S BET ) of cobaltic oxide (Co 3 O 4 ) are prepared by different methods, i.e., precipitation-oxidation, impregnation and hydrothermal. The effect of S BET of Co 3 O 4 on the catalytic property toward CO oxidation is investigated. The results indicate that the optimum S BET of Co 3 O 4 could increase the catalytic activity. Characterization of the cobaltic oxide using X-ray diffraction (XRD), N 2 -adsorption at )196°C, infrared (IR) and temperature-programmed reduction (TPR) reveals that the increase of S BET on Co 3 O 4 can weaken the bond strength of Co-O and promote more lattice oxygen desorption from Co 3 O 4 to cause the reduction become easy. We conclude that the S BET effect, caused by various prepared methods and refined conditions, are responsible for the activity enhancement of Co 3 O 4 . The T 50 (the conversion of CO reached 50%) is decreased significantly when the S BET is increased, i.e., PO-R230 > PO-C400 > I-C550 > H-150 $D-Strem.
Nanosized nickel oxide was synthesized by a simple liquid-phase process to obtain the hydroxide precursor and then calcined to form the oxide. The precursor and the nickel oxide were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis (TG) and temperature-programmed reduction (TPR). The results indicated that the particle size of nickel oxide was controlled by the calcined temperature (T C ). Mixed phases of nickel oxide and nickel hydroxide were present as the T C was lower than 300°C. Non-stoichiometric nickel oxide (NiO x , x = 1.2) was formed between 250°C and 400°C and a pure nickel oxide was formed as the T C arrived 500°C. The particle size of nickel oxide changed as the calcined temperature was controlled under 250°C, 300°C, 400°C and 500°C, the order was 5.6 nm, 6.5 nm, 11 nm and 17 nm, respectively.
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