La1.867Th0.100CuO4 was prepared by means of the citric acid complexing method. The reduction-oxidation (redox) properties of this composite oxide have been investigated by using the XRD, TGA, EPR, TPD, and SEM methods. The fresh (non-reduced) La1.867Th0.100CuO4 catalyst is single phase with tetragonal K2NiF4-type structure. There were three reduction steps observed over La1.867Th0.100CuO4 in the temperature ranges of 25-100, 100-300, and 300-500°C, respectively. After reduction at 300°C, the material still retained its original single phase but there were oxygen vacancies generated in the lattice. After reduction at 500°C, it decomposed to a mixture of oxides In the course of reduction, trapped electrons were generated. During the oxidation of the reduced sample, O2- was detected Apparently, oxygen vacancies are able to stabilise O2- on the surface of the catalyst. NO adsorption on both the fresh and reduced La1.867Th0.100CuO4 samples generated NO radicals and O2- species. On a La1.867Th0.100CuO4 sample reduced at 300°C, [O2NO2]2- was generated in NO adsorption and decomposed to N2 and O2- at ca. 730°C. After reduction, the O2- inside the La1.867Th0.100CuO4 lattice became more mobile and participated in the decomposition of [O2NO2]2-. The fresh (non-reduced) La1.867Th0.100CuO4 sample with cation defects in its lattice shows higher NO decomposition activity than the fresh La2CuO4 sample in which there are no cation defects. The 300°C-reduced La1.867Th0.100CuO4 with cation defects and oxygen vacancies is more active than the fresh one for NO decomposition. The redox action between Cu+ and Cu2+ is an essential process for NO decomposition.
|Number of pages||8|
|Publication status||Published - Mar 2000|
Scopus Subject Areas
- NO decomposition
- Redox behaviour