The Effect Of Oxygen Vacancy Concentration On The Properties Of Perovskite-type Catalysts

Two series of perovskite ype catalysts, LaCo05Fe05O3 . and LaCo047Fe047Pd006O3 . ( A means oxygen vacancy concentration) , were prepared by coprecipitation. Oxidation and reduction treatments were performed to the catalysts at different temperature to obtain catalysts with different oxygen vacancy concentration. These catalysts were studied with respect to their catalytic activities of CO, HC and NO. Moreover, the means of XRD, ICP ES, BET, SEO, TPR and XPS were also used to characterize the catalysts. The effects of oxygen vacancy concentration on the catalytic activity, structure, surface oxygen and activity of crystal oxygen were discussed. After reduction treatment, the amount of surface excess oxygen increased with the oxygen vacancy concentration, and the catalytic activity of CO was promoted. After oxidation treatment, the amount of surface excess oxygen increased with the treatment temperature but the oxygen vacancy concentration decreased, and the catalytic activity of CO was promoted, too. The concentration of Cobalt on the surface of catalysts increased after oxidation treatment that could account for the increasement of the amount of the surface excess oxygen. Oxygen vacancy concentration could promote both the adsorption of oxygen and the mobility of the crystal oxygen to improve the catalytic properties. Under the experiment condition: the catalyst which had been treated through hydrogen at 3000C had the best catalytic activity: the oxygen vacancy concentration was 0. 34, the temperature of 90% conversion to CO and NO are 2310C and 2130C respectively, the temperature of 80% conversion to I-IC is 4OOC0...