Catalytic functions of Y-Ba-Cu-O oxides. Catalytic decomposition and uptake of nitric oxide.

Abstract

A study has been made to utilize the oxygen vacancies of perovskite-like Y-Ba-Cu-O compounds as the catalytically active sites. Y-Ba-Cu-O compounds were found to have catalytic activity for NO decomposition, but they were deactivated at 800°C by sintering. Subsequently, MgO supported Y-Ba-Cu-O catalysts were prepared in order to increase the catalytic activity and to suppress sintering. The Y-Ba-Cu-O supported catalysts have a higher activity for NO decomposition than a commercial Pt supported catalyst at 800°C. XPS analysis suggests that the decomposition of NO is facilitated by the redox cycle of Cu (Cu+ Cu2+). It is also reported that a large quantity (2.53 in molar ratio) of NO was taken up at 573K and desorbed at 773K by YBa2Cu3O7-y. The uptake ratio of NO increased with increasing number of oxygen vacancies which were introduced by annealing in N2. The characteristic features of Y-Ba-Cu-O compounds shown above are ascribed to two-dimensional Cu-O plane with oxygen deficiency. The oxygen deficient Cu-O plane is stabilized by the lattice framework containing Ba2+ and Y3+.