Temperature-dependent chemical incompatibility between NiO-YSZ anode and alkaline earth metal oxides: Implications for surface decoration of SOFC anode

Alkaline earth metal oxides (AEMOs) have been recognized one of the most effective modifiers to alleviate coking issue of Ni-based anodes of solid oxide fuel cells (SOFCs). Nevertheless, the interaction between AEMOs and Ni-based anode matrix may also degrade the cell performance. In this work, the chemical compatibility between AMEOs and NiO-YSZ anode as well as their possible consequences were systematically investigated from both experimental and theoretical perspectives. XRD analyses reveal that the chemical compatibility of AEMOs with NiO-YSZ is temperature-dependent. The formation of alkaline earth metal (AEM) zirconates is detrimental to the oxygen ionic conductivity while the formation of AEMO-NiO solid solution suppresses the catalytic activity and electrical conductivity of Ni-YSZ anodes. The Ca, Sr and Ba enrichment in YSZ are observed, indicating the higher affinity of YSZ to AEMOs than that of NiO. Two potential strategies to preferentially deposit AEMO on Ni particles without chemical interaction are proposed. It is anticipated the findings in this work can provide guidance for designing Ni-based SOFC anode with both high-performance and anti-coking.