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A La0.6Sr0.4Co0.2F0.8O3 mixed ionic electronic conducting (MIEC) membrane was used in a dual chamber reactor for the promotion of the catalytic activity of a platinum catalyst for ethylene oxidation. By controlling the oxygen chemical potential difference across the membrane, a driving force for oxygen ions to migrate across the membrane and backspillover onto the catalyst surface is established. The reaction is then promoted by the formation of a double layer of oxide anions on the catalyst surface. The electronic conductivity of the membrane material eliminates the need for an external circuit to pump the promoting oxide ion species through the membrane and onto the catalyst surface. This renders this “wireless” system simpler and more amenable for large-scale practical application. Preliminary experiments show that the reaction rate of ethylene oxidation can indeed be promoted by almost one order of magnitude upon exposure to an oxygen atmosphere on the sweep side of the membrane reactor, and thus inducing an oxygen chemical potential difference across the membrane, as compared to the rate under an inert sweep gas. Moreover, the rate does not return to its initial unpromoted value upon cessation of the oxygen flow on the sweep side, but remains permanently promoted. A number of comparisons are drawn between the classical electrochemical promotion that utilises an external circuit and the “wireless” system that utilises chemical potential differences. In addition a ‚surface oxygen capture’ model is proposed to explain the permanent promotion of the catalyst activity. [ABSTRACT FROM AUTHOR]

Abstract: Y-doped BaCeO3 (BCY), a solid state ion conductor which exhibits mixed proton and oxide ion conductivity under some conditions, was used as an electrolyte in a solid oxide fuel cell (SOFC). The conductivities of 10% and 25% Y-doped BaCeO3 (BCY10 and BCY25) were measured under a single gas atmosphere of 5% hydrogen in argon (5% H2/Ar), air and pure argon (Ar). Furthermore, a dual-chamber SOFC reactor was used to investigate the conductivities of the BCY10 and BCY25 electrolytes under fuel cell conditions, i.e., 5% hydrogen in argon at the anode with air at the cathode. The performance of BCY-based SOFC with Pt electrodes was measured over a temperature range of 500–800 °C using a galvanostat/potentiostat. Both anode and cathode product stream compositions were analysed using a gas chromatograph and a hygrometer. A material balance for the system was performed in order to estimate proton and oxygen ion fluxes across the electrolyte. Water transport across the electrolyte in the absence of an external circuit was also studied. [Copyright &y& Elsevier]