Ni / GDC Fuel Electrode for Low Temperature SOFC and its Aging Behavior under Accelerated Stress

Abstract

For the increase of the number of the potential applications of SOCs as well as a lower system cost, realization of operating at lower temperatures (< 650 °C) is a key point. However, the overall cell performance would decrease dramatically with reduction in temperature because of reducing ionic conductivity in electrolyte and increased polarization resistance from both electrodes. In case of realizing high performance yet also good mechanical stability, wet infiltration is shown to be one effective method [1].In this contribution, the concept of infiltration is presented with a GDC infiltrated Ni-Skeleton fuel electrode. With this approach, a polarization resistance of below 0.2 Ω cm² at 600 °C is realized. To study the durability of such electrode, the concept of accelerated testing is applied. Symmetrical cells are tested to avoid an additional impact of the air electrode [2]. The cells are operated at temperatures up to 900 °C and a high steam content of 50 % for up to 1000 h. Electrochemical impedance spectroscopy (EIS) is employed to record the temporal development of the electrode performance. By means of the distribution of relaxation times (DRT), the temporal evolution of the loss processes is identified. As an example, impedance and DRT at 600 °C before and after aging at 900 °C for 650 h is presented in Figure 1(c). Microstructural analysis of electrode in different aging status is carried out with optical- and electron microscopy. The initially nanoscaled microstructure of the infiltrated GDC, as presented in Figure 1(a), is agglomerated (Figure 1(b)) during aging at elevated temperatures, which is in agreement with the observed increase in polarization resistance.KeywordsSolid Oxide Fuel Cell; low temperature; porous electrodes; accelerated life time test; aging phenomenon; GDC; SEM[1] Z. Liu.et al., J. Power Sources, 237, p. 243 (2013)[2] C. Endler-Schuck.et al., J. Power Sources, 196 (17), p. 7257 (2011).[3] S. Dierickx.et al., Electrochim ica Acta, 355, p. 136764 (2020).[4] A. Weber, tm - Technisches Messen, 88 (1), p. 1 (2021).[5] C. Grosselindemann.et al., ECS Trans., 103 (1), p. 1375 (2021). Figure 1