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 forNOelimination 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.

Perovskite-type oxides La1−xA′xCo1−yBiyO3−δ (A′x=Ba0.2, Sr0.4; y=0, 0.2) and La1−xSrxMO3−δ (M =Co0.77Bi0.20Pd0.03, x=0, 0.2, 0.4) and perovskite-like oxides La1.867Th0.100CuO4−δ, Nd2−xA xCuO4−δ (A′x=Ba0.4, Ce0.2), and YBa2Cu3O7−δ have been investigated as catalysts forCOoxidation, NO removal, andN2Odecomposition, respectively. X-ray diffraction results revealed that (i) all of these materials were single phase, and (ii) the crystal structures of La1−xA′xCo1−yBiyO3−δ, La1−xSrxMO3−δ, La1.867Th0.100CuO4−δ, Nd2−xA′xCuO4−δ, and YBa2Cu3O7−δ were cubic, orthorhombic, tetragonal (T structure), tetragonal (T′structure), and orthorhombic, respectively. The results of chemical analysis indicated that (i) there were Co4+/Co3+ ions in La1−xA′xCoO3−δ (A′x=Ba0.2, Sr0.4), Co2+/Co3+ and Bi5+/Bi3+ ions in La1−xA′xCo0.8Bi0.2O3−δ(A′x=Ba0.2, Sr0.4) and La1−xSrxMO3−δ, Cu2+/Cu3+ ions in La1.867Th0.100CuO4−δ, Nd2CuO4−δ, Nd1.6Ba0.4CuO4−δ, and YBa2Cu3O7−δ; and (ii) after pretreatments in H2 or helium at certain temperature, Cu+/Cu2+ ion couples appeared in these cuprate samples. Oxygen isotope exchange experiments indicated that the lattice oxygen mobility in the Bi-doped catalysts were much higher than that in the Bi-free ones. TPR results showed that lattice oxygen in the former samples could be reduced at temperatures lower than those in the latter samples. In the oxidation of CO, the Bi-incorporated catalysts performed much better than the corresponding Bi-free catalysts, the Sr-substituted perovskites showed higher catalytic activities than the Ba-substituted ones; among La1−xSrxMO3−δ, La0.8Sr0.2MO2.90 exhibited the best catalytic activity. The improved catalytic performance due to the Sr (or Ba)- and Bi-doping is believed to be associated with the enhancements in oxygen vacancy density and Con+/Co(n+1)+ (n=2, 3) and Bi3+/Bi5+ couple redox ability as well as in lattice oxygen mobility. In the elimination of NO over La1−xSrxMO3−δ, La0.8Sr0.2MO2.90 performed the best. The 300℃-reduced La1.867Th0.100CuO4− catalyst that possessed dual cationic and anionic defects and Cu+/Cu2+ couple showed higher DeNO activity than the fresh one; the redox action between Cu+ and Cu2+ is an essential process for NO decomposition. In the decomposition of N2O, the 800 ◦C-treated Nd2−xA xCuO4−δ (A'x=Ba0.4, Ce0.2) and YBa2Cu3O7− samples were superior in catalytic performance to their fresh counterparts; oxygen vacancies were favorable for the formation of the crucial N2O2 2− intermediate species in N2O activation, and the redox Cup+/Cu(p+1)+ (p=1 and 2) couples involved in the N2O decomposition processes. The DeN2O activity over the Ce- or Ba-doped catalyst was much better than that over the undoped catalyst (Nd2CuO4−δ). This behavior is intimately related to the oxygen nonstoichiometry and copper ion redox properties. According to the outcome of our experiments, we conclude that there is a strong correlation either between the structural defect (mainly oxygen vacancies) and catalytic activity or between the redox [Con+/Co(n+1)+ (n=2, 3), Bi3+/Bi5+, and Cup+/Cu(p+1)+ (p=1 and 2) couples] ability and catalytic performance of these materials for CO and NOx removal. The generation of oxygen vacancies by A-site replacements favors the