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 CeP(2)O(7) thin plates, which are sintered at 300-900 degrees C, the 450 degrees C CeP(2)O(7) 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 x 10(-2)S cm(-1) at 180 degrees C. When 10 mol% Mg is doped on the Ce site of CeP(2)O(7), the maximum conductivity is raised to 4.0 x 10(-2)S cm(-1) at 200 degrees C. The Mg doping not only raises the conductivity, but also shifts and widens its temperature window for electrolyte applications. Ce(0.9)Mg(0.1) P(2)O(7) is considered a more appropriate composition, with conductivity > 10(-2)S cm(-1) between 160 and 280 degrees C. Accordingly, a hydrogen-air cell is built with the Ce(0.9)Mg(0.1) P(2)O(7) electrolyte and its performance is measured. The fuel cell generates electricity up to 122 mA cm(-2) at 0.33 V using 50% H(2) at 240 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.