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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]

Abstract: A novel approach to electrochemical modification of catalytic activity using a wireless configuration has been undertaken. This paper presents preliminary results on the modification of a platinum catalyst film supported on a pellet of Sr0.97Ce0.9Yb0.1O3−δ (SCYb), considered to be a mixed protonic–electronic conductor under reducing conditions. The wireless configuration utilises the mixed ionic and electronic conductivity of the supporting membrane to supply an ionic promoting species to the catalyst surface. Control of the flux of this species is achieved by adjusting the effective hydrogen chemical potential difference across the membrane in a dual-chamber reactor with one chamber acting as the “reaction side” and the other as the “sweep side”. The reaction rate can be promoted by up to a factor of 1.6, for temperatures around 500 °C and low reactant concentrations, when hydrogen is introduced on the sweep side of the membrane reactor. The use of helium, moist helium and oxygen in helium as sweep gases did not modify the reaction rate. [Copyright &y& Elsevier]

Abstract: The recently discovered, high-temperature proton conductor, La0.99Sr0.01NbO4−δ , was used as a support for the electrochemical promotion of a platinum catalyst. Ethylene oxidation was used as a probe reaction in the temperature range 350–450°C. Moderate non-Faradaic rate modification, attributable to a protonic promoting species, occurred under negative polarisation; some permanent promotion was also observed. In oxidative atmospheres, both the of the reaction mixture and the temperature influenced the type and magnitude of the observed rate modification. Rate-enhancement values of up to ρ =1.4 and Faradaic-efficiency values approaching Λ =−100 were obtained. Promotion was observed under positive polarisation and relatively dry, oxygen-rich atmospheres suggesting that some oxygen ion conductivity may occur under these conditions. Impedance spectroscopy performed in atmospheres of 4kPa O2/N2 and of 5kPa H2/N2 under dry and slightly humidified (0.3kPa H2O) conditions indicated that the electrical resistivity is heavily dominated by the grain-boundary response in the temperature range of the EPOC studies; much lower grain-boundary impedances in the wetter conditions are likely to be attributable to proton transport. [Copyright &y& Elsevier]