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648b

An Oxide Ion and Proton Co-Ion Conducting Electrolyte for Intermediate-Temperature Fuel Cells

Chunsheng Wang and Xilin Chen. Department of Chemical & Biomolecular Engineering, University of Maryland, 1223A Chemical and Nuclear Engineering, College Park, MD 20742

The ionic conductivity of Sn0.9In0.1P2O7 ceramic was investigated under various atmospheres within the temperature range of 130-230oC. Similar to mixed-conductive perovskite oxides at high temperatures (such as SrCe0.95Yb0.05O3-, La0.9Sr0.1Ga0.8Mg0.2O3- at 600-1000oC), Sn0.9In0.1P2O7 can conduct both protons and oxide-ions at low temperatures (130-230oC). The conductivity of Sn0.9In0.1P2O7 reaches 0.019 S/cm at 200oC in wet nitrogen. Its transport numbers determined by steam concentration cells are about 0.8 for proton and 0.1 for oxide-ion. The performance of direct methanol fuel cells at 170oC using mixed-ion conductive Sn0.9In0.1P2O7 electrolyte is higher than that at 235oC using pure proton conductive CsH2PO4 electrolyte. This is attributed to direct oxidation of CO at the anode by the oxide-ions generated at the cathode and moved through the Sn0.9In0.1P2O7 electrolyte.