287939 Catalytic Activity in Un-Doped and Rare Earth-Doped Strontium Cerates
Following Iwahara’s report in 1981 , acceptor-doped strontium cerates (SrCe1-xMxO3-δ) have been studied as high-temperature protonic conductors (HTPCs). The substitution of Ce4+ with trivalent cations (M3+) leads to the formation of charge-compensating oxygen-ion vacancies (δ), which may react with gas-phase steam or oxygen leading to the incorporation of protonic or p-type electronic conductivity, respectively. Mixed protonic and electron-hole conductivity in Yb-doped SrCeO3 enabled its application as both membrane and catalyst in an electrochemical reactor for the non-oxidative coupling of methane to form C2-hydrocarbons . However, SrCeO3-based materials have not been studied from a purely catalytic standpoint, either as active catalysts or as supports. A significant body of work though has been carried out on oxygen-ion conducting oxides as catalysts . Recent studies have also reported catalytic activity in the related class of BaCeO3-based materials [4, 5].
The objective of the present study was to document inherent catalytic activity in un-doped SrCeO3, and its evolution upon doping with different trivalent, rare earth cations. Powders of the oxides were synthesized from the respective precursors using the conventional technique of solid-state reaction. Carbon monoxide oxidation and water-gas shift were selected for the investigation. The reactions were carried out between operating temperatures of 400 and 1000oC. In addition to atmosphere and operating temperature, the choice of dopant has also been demonstrated to influence the electrochemical properties of SrCeO3 . Hence, any variation in catalytic activity observed with respect to the dopant would enable deductions regarding the dependence of reaction mechanism on the protonic and electronic conductivities in the oxides.
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