Co-based perovskites

An alternative to the Co-rich perovskites is the Sr-doped LaFe03 which has a lower thermal expansion coefficient and a superior chemical compatibility with doped Ce02 electrolyte. LaFe03 is expected to be more stable than Ni- and Co-based perovskites because the Fe3+ ion has the stable electronic configuration 3d5. It is, therefore, expected that compositions in the system (La,Sr)(Co,Fe)03 will have desirable properties for intermediate temperature SOFC cathode applications. 

The TPR profiles of five Co-based perovskites prepared by reactive grinding with ZnO as additive for different milling times are shown in Figure 4(a-e), Figure 4f represents a LaCoOs perovskite prepared by the citrate method (referenee sample). 

A series of perovskites were prepared but care must be taken in preparing these perovskites as it has been shown that composition and structure of these perovskites are highly dependent on the preparation route and the presence/concentration of dopants is critical. If all the perovskites studied here have a defective structure, then it is believed that the Co based perovskites with minor phases such as ceria, lanthana and cobalt oxide offer the most promise for catalytic application. PXRD analysis shows the presence of... 

It is well known that the catalysts, Pt-family, transition-metal oxides, LaB03(B Mn, Co)-based perovskite-type oxide [5], metal-nitride, metal-sulfide, and organometallic compounds, show direct 4-electron oxygen reduction mechanism. 

Suard, E., Fauth, F., Caignaert, V., Mirebeau, I., and Baldinozzi, G. (2000) Charge ordering in the layered Co-based perovskite HoBaCo20s. Phys. Rev. B,... 

Reducible metal oxides, which are able to provide their lattice oxygen for methane activation, are potential catalytic materials for alternating feeding of CH4 and O2. Mn- and Co-based perovskites were identified as effective catalysts for such OCM operation [24]. At best, the yield of C2 hydrocarbons of 20% with the corresponding selectivity of 73% was obtained at 1073 K over S1C0O3 doped with the oxides or hydroxides of K and Na applying a 1.5-min cycle of methane. However, the catalyst productivity remained still low. 

Wallin M, Cruise N, Klement U, Palmqvist A, Skoglundh B. (2004). Preparation of Mn, Fe and Co based perovskite catalysts using microemulsions. Colloid Surface A. 238, 27-35. 

---