Sr doping effect on the structure property and NO oxidation performance of dual-site doped perovskite La(Sr)Co(Fe)O3

In this work, the physico-chemical properties of the La1-xSrxCo0.8Fe0.2O3 (x = 0, 0.3, 0.4, 0.5, 0.6) catalysts were systematically studied as well as their catalytic activity for NO oxidation. When Sr2+ substituted at La3+ site, [CoO6] octahedral distortion is amended and the crystal structure transited from rhombohedral to cubic. Co (III) electronic configuration turned from high/intermediate spin state to low spin sate with empty e(g) filling. Imbalanced positive charge induced by Sr2+ was compensated by tetravalent Co(IV) ions and oxygen deficiencies together. All these factors resulted in better reducibility of Co, increasing oxygen deficiencies and more mobile oxygen species. Thus, NO conversion of 67-69% was attained over the Sr-doped catalysts at 300 degrees C, much higher than the undoped catalysts (NO conversion of 24.3%). A significant decrease of the apparent activation energy (E-a), from 68 kJ/mol down to similar to 52 kJ/mol, was observed as well. Based on the kinetics results, NO oxidation over the perovskite catalysts is a typical superficial process determined by adsorbed NO and surface oxygen species.

Automated summary

By systematically studying the physico-chemical properties of La1-xSrxCo0.8Fe0.2O3 catalysts, it was found that Sr doping improved the reducibility of Co and oxygen deficiencies, resulting in significantly increased NO conversion rates. This improvement in catalytic activity was attributed to a surface process determined by adsorbed NO and surface oxygen species.