Effect of various sintering inhibitors on the long term performance of Ni-YSZ anodes used for SOFCs

Sintering of Ni in solid oxide fuel cell (SOFC) anodes (Ni-YSZ) is a major cause of anode degradation. To reduce this growth rate, several sintering inhibitors (SiC, SiN, Al2O3, AlN, CeO2 and GDC) were added into Ni-YSZ anode using powder methods. The modified anodes were screen printed on YSZ electrolyte to prepare symmetric half-cells and their performance was investigated by long term stability test at high temperature. X-ray diffraction (XRD) analysis showed that the most sintering inhibitors were chemically compatible with anode materials except Al2O3 and AlN. During the long term test, area specific resistance (ASR) was measured at 1000 °C in 25vol% H2 and 75vol% N2 environment. Triple phase boundary (TPB) density was calculated by image analysis techniques before and after operation. A clear relation was found between ASR change rate determined from electrochemical measurements and TPB density change rate calculated from image analysis. Moreover, among the various sintering inhibitors, CeO2 and GDC exhibited the best performance by showing the lowest ASR and TPB density change rates. ASR change rate has been discussed in view of loss in TPB density during operation.