Cerium Pyrophosphate-based Proton-conducting Ceramic Electrolytes for Low Temperature Fuel Cells

Abstract

Acceptor-doped cerium pyrophosphates have shown significant proton conductivity of >10 -2 S cm -1 in the range of 100 - 300oC and are considered promising candidates for use as electrolytes in proton-conducting, ceramic electrolyte fuel cells (PCFCs). But, cerium pyrophosphates themselves do not have structural protons, and protons incorporate into their material bulk only as impurities on exposure to a hydrogen-containing atmosphere. However, proton incorporation and proton conduction in these materials are expected to be affected by factors such as the nature (ionic size and charge) and concentration of the aliovalent dopant, processing history (synthesis route and microstructure), and the presence of residual phosphorous phosphate P m O n ) phases. An exact understanding of these aspects has not yet been achieved, leading to large differences in the magnitude of proton conductivity of cerium pyrophosphates reported in various studies. Herein, we systematically address some of these aspects, and present an overview of factors affecting proton conductivity inacceptor-doped CeP 2 O 7 .