Understanding Oxygen Release from Nanoporous Perovskite Oxides and Its Effect on the Catalytic Oxidation of CH4 and CO

The design of nanoporous perovskite oxides is considered an efficient strategy to develop performing, sustainable catalysts for the conversion of methane. The dependency of nanoporosity on the oxygen defect chemistry and the catalytic activity of perovskite oxides toward CH4 and CO oxidation was studied here. A novel colloidal synthesis route for nanoporous, high-temperature stable SrTi0.65Fe0.35O3-delta with specific surface areas (SSA) ranging from 45 to 80 m(2)/g and pore sizes from 10 to 100 nm was developed. High-temperature investigations by in situ synchrotron X-ray diffraction (XRD) and TG-MS combined with H-2-TPR and Mossbauer spectroscopy showed that the porosity improved the release of surface oxygen and the oxygen diffusion, whereas the release of lattice oxygen depended more on the state of the iron species and strain effects in the materials. Regarding catalysis, light-off tests showed that low-temperature CO oxidation significantly benefitted from the enhancement of the SSA, whereas high-temperature CH4 oxidation is influenced more by the dioxygen release. During isothermal long-term catalysis tests, however, the continuous oxygen release from large SSA materials promoted both CO and CH4 conversion. Hence, if SSA maximization turned out to efficiently improve low-temperature and long-term catalysis applications, the role of both reducible metal center concentration and crystal structure cannot be completely ignored, as they also contribute to the perovskite oxygen release properties.

Automated summary

The design of nanoporous perovskite oxides is an efficient strategy for developing sustainable catalysts for methane conversion, with their porosity influencing oxygen defect chemistry and catalytic activity. The synthesis of nanoporous materials with specific surface areas and pore sizes was developed, and high-temperature investigations showed improvements in oxygen release and diffusion. Catalytic tests demonstrated benefits in CO and CH4 conversion, with continuous oxygen release promoting long-term catalytic applications. The role of reducible metal center concentration and crystal structure also contribute to perovskite oxygen release properties.