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

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, Ce_1-xMn_xP₂O₇ (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. Ce_0.9Mn_0.1P₂O₇ 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 Ce_0.9Mn_0.1P₂O₇ 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

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