A comparative investigation on protonic ceramic fuel cell electrolytes BaZr0.8Y0.2O3-δ and BaZr0.1Ce0.7Y0.2O3-δ with NiO as sintering aid

Abstract

Solid oxide fuel cells based on proton-conducting ceramic electrolytes, i.e., protonic ceramic fuel cells (PCFCs), are promising in operating at intermediate to low temperature. BaZr0.8Y0.2O3-δ (BZY) and BaZr0.1Ce0.7Y0.2O3-δ (BZCY) are two typical electrolyte materials for PCFCs. However, there is still a lack of basis for making a choice between the two materials. In this paper, we present a comparison investigation on practical BZY and BZCY electrolytes with NiO of 2 mol.% as sintering aid. Their crystal structure, sinterability, microstructure, and electrical conductivity in humid air and hydrogen (3% H2O) are measured and analyzed. Anode-supported PCFCs based on the two electrolyte materials are prepared and their electrochemical performances are tested and analyzed in association with an examination on their microstructure. The results show that both materials can be densified after sintered with NiO aid at 1400 °C for 6h. Ni is doped into the interstitial of BZY while it occupies the B site of perovskite lattice of BZCY. The sintered BZY has small grains and many grain boundaries while BZCY has large grains and much fewer grain boundaries, resulting in lower conductivity of BZY than that of BZCY. A PCFC with BZY electrolyte gives a peak power density of 360 mW cm−2 at 700 °C, while this value for a PCFC with BZCY is 855 mW cm−2. Although the performances of BZCY seems much better than those of BZY, a stability test in 10% CO2-containing Ar at 650 °C shows BZY is stable while BZCY reacts with CO2 to form BaCO3 and CeO2.