| Current low temperature fuel cells require expensive precious catalysts and are restricted to operation on carbon monoxide and sulfur free hydrogen or methanol fuel. High operating temperatures (800--900°C) of solid oxide fuel cells (SOFC) eliminate these problems and offer a variety of advantages, including waste heat utilization, fast and reversible electrode reactions and the capability to operate on a variety of fuels. However these high temperatures also complicate sealing, necessitate expensive construction materials and can limit lifetime. The growing interest in proton conducting oxides is driven by the desire to reduce the operating temperature to the intermediate range of 500--600°C. Fuel cells operating in this range would maintain the benefits of high temperature and gain the advantages of lower temperature operation.;Perovskite structured oxides in the series BaCe1-x-zZr x(Y,Yb)zO3--delta are among the most promising materials for application as the electrolyte in intermediate temperature proton conducting SOFC (H+-SOFC). These materials have shown technologically relevant proton conductivity in the target temperature range. The primary barriers to their application are stability in CO2 containing atmospheres, low grain boundary conductivity and the high sintering temperature required to produce dense electrolytes, typically >1700°C.;In this work, novel proton conducting materials were synthesized and their stability and conductivity were tested for application as SOFC materials. Measurements in a hydrogen concentration cell indicated that the material is an almost pure ionic conductor at the temperatures of interest.;Fuel cell operation with hydrogen fuel, as well as via internal steam reforming of methanol and ethanol, was successfully demonstrated with Ni, Cu-Ni and Cu anode catalysts, though significant carbon deposition was observed on a Ni-based catalyst in ethanol/water feed. Highest fuel cell performance was observed when using Ni catalyst, which was attributed to a higher catalytic activity of Ni towards fuel oxidation and hydrocarbon reforming reactions.;Finally, the reversibility of manufactured H+-SOFCs was investigated by performing high temperature electrolysis. Further long-term and electrode studies are necessary to reduce the overpotentials required to drive the electrolysis reaction. |
