Promotion Effects And Mechanism Of Alkali Metals And Alkaline Earth Metals On Cobalt-cerium Composite Oxide Catalysts For N_20 Decomposition

摘要

A series of alkali metal- and alkaline earth metal-doped cobalt-cerium composite oxide catalysts were prepared by the citrate method and tested for the decomposition of N_20. Strong promotion effects of alkali and alkaline earth metals on the activity of the catalyst were obtained in the order Li < Na < K < Rb < Cs and Mg < Ca < Sr, Ba. The promotion effects of alkaline earth metals were much weaker than the effects of alkali metals. To investigate the origin of the promotion effect. X-ray diffraction, Brunauer-Emrnett-Teller surface area measurement, X-ray photoelectron spectroscopy, temperature-programmed desorption, and hydrogen temperature-programmed reduction methods were used to characterize the alkali metal-doped catalyst. The analytical results indicated that alkali metals improved the redox ability of active site Co~(2+) by acting as electronic promoters. Catalytic decomposition of N_2O proceeds through an oxidation-reduction mechanism with participation of electrons from Co~(2+), thus the increase in the redox ability of Co~(2+) should lead to an increase in the activity of the catalyst.