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

Abstract

Cerium pyrophosphate based solid state proton conducting materials with ionic conductivity >10-2 S cm-1 in 100-250 oC range have immense importance in fuel cells.1-5 In this work, Ce1-xMnxP2O7 (CMP) (x=0.05, 0.075, 0.1, 0.125 and 0.15) composite electrolytes are synthesized by two-step slow digestion method with different P/(Ce+Mn) molar ratio.4 The CMP samples with high phosphate content become denser on sintering. The variation of ionic conductivity with temperature is studied in dry and humidified air for the potential application of CMPs as electrolytes in proton-conducting ceramic electrolyte fuel cells. Among various CMP samples, CMP-100-2.7P (i.e. Ce0.9Mn0.1P2O7 with P/(Ce+Mn)=2.7) shows maximum conductivity of 6.54X10-6 S cm-1 at 450 oC in dry air and 1.78X10-2 S cm-1 at 170 oC in humidified air (pH2O= 0.12 atm). The ionic conductivity of CMPs increases with the increasing pH2O and CMP-100-2.7P shows maximum conductivity of 2.24X10-2 S cm-1 at 170 oC in pH2O=0.16 atm.Figure. (a) SEM images of fractured section of 400 oC sintered pellets of Ce0.9Mn0.1P2O7 samples with different initial P/(Ce+Mn) ratio; Temperature dependence of ionic conductivity of various CMP samples with different dopant concentration in (b) dry air and (c) humidified air (pH2O =0.12 atm) condition. References B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Electrochem. Soc., 159, F819 (2012).B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Phys. Chem. C, 117,2653 (2013).B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Alloys Compd., 578, 279 (2013). B. Singh, S. Y. Jeon, J. H. Kim, J. Y. Park, and S. J. Song, (Submitted in J. Electrochem. Soc.). C. Chatzichristodoulou, J. Hallinder, A. Lapina, P. Holtappels, and M. Mogensen, J. Electrochem. Soc., 160, F798 (2013).