Transition perovskite, reducing process

Reduction of NO with CO or H2 was found to be an interesting example of intrafacial catalytic process (30). If this reaction is conducted over a transition-metal oxide, the reaction rate appears to be related primarily to the thermodynamic stability of the oxygen vacancies adjacent to a transition metal ion. Associative as well as dissociative adsorption of NO have been reported on perovskite oxides (14, 22, 80, 174) (see also Section VI,B) the adsorption on the reduced oxides is stronger than in the oxidic compounds. Dissociative adsorption takes place at moderate temperatures as in NO reduction over Lao.gsBao.isCoOs at 100°C with the subsequent formation of N2 and N20 (73). 

Perovskites containing a transition metal are of particular interest because of the availability of multiple oxidation states, which facilitate electrocatalytic processes and provide mechanisms for electronic conductivity. For example, under reducing atmospheres the transition metal ions change to lower oxidation states, effectively freeing up electrons to pass current. Typical examples of such species are titanium, niobium, and vanadium. SrNbOs has an electronic conductivity of 10" Scm under reducing conditions [14], and Petrie reported a conductivity of 10 cm for SrVOs under similar conditions [15]. Unfortunately, it was also found that these compounds could not be fabricated in air. 

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