Active coordination sites of Co spinel oxides for NO reduction by CO

Cobalt spinel oxides, containing octahedral (Oh) and tetrahedral (Td) sites, exhibit high activity for NO reduction by CO. The active sites of cobalt spinel oxides for NO-CO reaction was identified using various cobalt spinel oxides having different CoOh/CoTd ratio. Comparing the CoOh/CoTd ratio determined by EXAFS fitting analysis and the rate of NO reduction, it was clarified that octahedral site is responsible for NO reduction by CO. Furthermore, synchrotron-based in-situ XAFS measurements unveiled the contribution of CoOh sites: The cobalt spinel oxides with high CoOh fraction were more easily reduced by CO to form oxygen vacancies than those with low CoOh fraction, and resulted in the higher activity for NO reduction by CO.

Automated summary

Cobalt spinel oxides with octahedral (Oh) and tetrahedral (Td) sites show high activity in NO reduction by CO. By studying cobalt spinel oxides with different CoOh/CoTd ratios, it was determined that the octahedral site is responsible for the NO-CO reaction. In-situ XAFS measurements revealed that cobalt spinel oxides with higher CoOh fraction are more easily reduced by CO, leading to higher activity in NO reduction by CO.