Proton-Conducting Ce0.9Mn0.1P2O7 Composite Electrolytes for Low Temperature Ceramic Electrolyte Fuel Cells

Abstract

Composites of 10% Mn2+-doped cerium pyrophosphate with excess phosphates were synthesized by a digestion method with different P/(Ce+Mn) molar ratios. The sintering at 400 oC leads to the formation of a proton-conducting composite of pyrophosphate, metaphosphate, polyphosphate and orthophosphate. The composites with high phosphate content become denser on sintering. The variation of ionic conductivity with temperature is studied in unhumidified and humidified air for the potential application as electrolytes in proton-conducting ceramic-electrolyte fuel cells (PCFCs). Among various samples, Ce0.9Mn0.1P2O7 with P/(Ce+Mn)=2.8 shows maximum conductivity of 7.49´10-6 S cm-1 at 450 oC in unhumidified air. In humidified atmosphere (pH2O=0.12 atm), Ce0.9Mn0.1P2O7 with P/(Ce+Mn)=2.3 shows maximum ionic conductivity (9.58´10-3 S cm-1) at 90 oC while those with P/(Ce+Mn)=2.7 and 2.8 show maximum ionic conductivities (1.78´10-2 and 1.86´10-2 S cm-1, respectively) at 170 oC.