Proton conductors of cerium pyrophosphate for intermediate temperature fuel cell

The crystal structure and proton conductivity of cerium pyrophosphate are investigated to explore its potential electrolyte applications for intermediate temperature fuel cell. Among the CeP2O7 thin plates, which are sintered at 300–900 °C, the 450 °C CeP2O7 sample exhibits superior proton conductivity under humidified conditions. Its conductivity, measured with impedance spectroscopy, is higher than 10−2 S cm−1 in the intermediate temperature range, with a maximum value 3.0 × 10−2 S cm−1 at 180 °C. When 10 mol% Mg is doped on the Ce site of CeP2O7, the maximum conductivity is raised to 4.0 × 10−2 S cm−1 at 200 °C. The Mg doping not only raises the conductivity, but also shifts and widens its temperature window for electrolyte applications. Ce0.9Mg0.1P2O7 is considered a more appropriate composition, with conductivity >10−2 S cm−1 between 160 and 280 °C. Accordingly, a hydrogen–air cell is built with the Ce0.9Mg0.1P2O7 electrolyte and its performance is measured. The fuel cell generates electricity up to 122 mA cm−2 at 0.33 V using 50% H2 at 240 °C.

► We explore the proton conductivity of cerium pyrophosphate and demonstrate it is a potential electrolyte for intermediate temperature fuel cell. ► The maximum conductivity of 450 °C-sintered CeP2O7 measures 0.03 S cm−1 at 180 °C, with a temperature window 120–190 °C for electrolyte applications. ► Doping 10 mol% Mg on the Ce site raises the maximum conductivity to 0.04 S cm−1 (200 °C), and widens the temperature window, 160–280 °C.