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N2 yield on Ba0.8La0.2Mn0.8Mg0.2O3 decreased from 70% to 30% on the addition of 1% CO2, which is a much larger negative effect than that seen with O2. The CO2 negative effects are not permanent and this may result from the inhibition of NO adsorption. Co-feeding of H2 as a reductant is effective for increasing NO conversion. This suggests that the catalyst surface was covered with strongly adsorbed nitrate or nitride species which formed by adsorption of NO on oxygen formed by the decomposition of NO, and the removal of this surface species might be the most important step for the NO decomposition reaction. Co-feeding of H2 is also effective for increasing the NO decomposition activity in the presence of CO2. The reaction mechanism was studied by IR measurements which also revealed that the surface of the catalyst was covered with strongly bound nitrate species (NO3−). The addition of H2 to the reaction mixture is effective for NO3− removal and so accelerates the NO decomposition under coexistence of CO2.

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NO direct decomposition on doped SrFeO3 perovskite oxide was investigated. The ability of SrFeO3 for direct decomposition of NO is strongly affected by the dopant in Fe sites. Among the examined dopants and compositions, the highest yield of N2 was achieved on SrFe0.7Mg0.3O3. When SrFe0.7Mg0.3O3 was loaded with Pt, the N2 yield further improved, and the light-off temperature fell by 100 K. On this catalyst, the yields of N2 and O2 were 56 and 35%, respectively, at 1123 K. On the Pt-loaded SrFe0.7Mg0.3O3 catalyst, the NO decomposition rate increased with increase in the NO partial pressure with PNO1.31. The presence of oxygen slightly decreased the N2 yield with PO2−0.12. Therefore, the effect of oxygen poisoning on NO decomposition upon Pt-loaded SrFe0.7Mg0.3O3 is small. From the result of O2-TPD, Pt loading possibly weakens the adsorption strength of surface oxygen and enhances NO adsorption. In summary, this study shows that the substitution of Fe with lower valence cation in SrFeO3 and also loading a small amount of Pt are highly effective for increasing the NO decomposition activity.

Study of the NO decomposition activity of the Ruddlesden–Popper-type oxide Sr3Fe2O7 doped with Ba and Zr revealed that Sr3Fe2O7 exhibits a high NO decomposition activity. Doping Ba and Zr for the Sr and Fe sites, respectively, is highly effective for improving NO decomposition activity. A high N2 yield of 72% is achieved at 1123 K and a N2 yield of 32% is sustained under a 2.5% oxygen cofeeding condition.