An investigation on the utilization of perovskite-type oxides La1−xSrxMO3 (M = Co0.77Bi0.20Pd0.03) as three-way catalysts

The perovskite-type oxides La1−xSrxMO3 (M=Co0.77Bi0.20Pd0.03) have been investigated for three-way catalytic performance and characterized by means of temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalysts exhibited good activity in CO elimination: La0.8Sr0.2MO3 showed ca. 100% CO conversion at 160°C, 60 000 h−1, and λ=1.00. Under similar reaction conditions, the activity for C3H6 elimination decreased in the order of La0.2Sr0.8MO3>La0.8Sr0.2MO3>La0.4Sr0.6MO3>La0.6Sr0.4MO3>LaMO3, while the activity for NO elimination decreased in the order of La0.8Sr0.2MO3>La0.2Sr0.8MO3>La0.4Sr0.6MO3>La0.6Sr0.4MO3>LaMO3. With x<0.6, La1−xSrxMO3 were single-phase and hexagonal in structure; at x=0.6 and 0.8, they were cubic and there was a trace amount of the La2O3 phase. The results of TPD, TPR, and XPS studies revealed the coexistence of over-stoichiometric oxygen vacancies in La0.8Sr0.2MO3, a criterion for good three-way catalytic performance.