Alternative SOFC Anode Materials with Ion- and Electron-Conducting Backbones for Higher Fuel Utilization

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2016-02; no. 39; p. 2886
• Main Authors: Futamura, Shotaro, Shen, Xuesong, Tachikawa, Yuya, Shiratori, Yusuke, Taniguchi, Shunsuke, Sasaki, Kazunari
• Format: Journal Article
• Language: English
• Published: 01.09.2016
• ISSN: 2151-2043; 2151-2035
• DOI: 10.1149/MA2016-02/39/2886

Introduction &Solid oxide fuel cells (SOFC) have a great potential to generate electricity with a high efficiency. Currently, Ni-YSZ cermet is widely used as the SOFC anode material. As anode Ni can be oxidized under a high fuel utilization, however, SOFC fuel can not be fully used. In this study, we analyzed alternative anode materials composed of GDC (Ce 0.9 Gd 0.1 O 2 ; ionic conductor), LST (Sr 0.9 La 0.1 TiO 3 ; electronic conductor), both of which act as stable ion- and electron-conducting frameworks, respectively, and Ni acts only as an electrocatalyst, as described in Fig. 1. Experimental &Electrolyte-supported cells with ScSZ (10 mol % Sc 2 O 3 -1 mol % CeO 2 -89 mol % ZrO 2 ) plate (20 mmφ×&0.2 mm t ) were used in this study. Mixture of LST and GDC (1 : 1 ; vol. %) was used for the anode and was sintered at 1300 o C for 3 h. Mixture of (La 0.8 Sr 0.2 ) 0.98 MnO 3 (LSM) and ScSZ with a weight ratio of 1:1 was used for the cathode. In order to further improve the anodic performance, Ni nanoparticles were impregnated into the porous LST-GDC composite anode. Electrode area was 8×&8 mm 2 and Pt mesh was used as the current collector. Cell performance such as I-V characteristics, anodic overvoltage, and anode-side ohmic loss were measured at 800 o Cby feeding humidified fuel. The amount of the catalytic Ni loading was optimized through the I-V measurements, FESEM analysis, and Red-Ox cycling tests. Results and discussion &The optimized amount of Ni loading was difficult to be judged only from the I-V measurements and the SEM figures because there were no obvious difference in the anode performance of the cells impregnated more than 0.0833mg-Ni/cm 2 . Then, Red-Ox cycling tests were conducted according to the procedure shown in Fig. 2, in order to investigate the stable distribution in which Ni catalytic particles are difficult to aggregate. As a result, the best Ni loading in this study was 0.0833mg-Ni/cm 2 for which anode voltage degradation was only 2% after 50 Red-Ox cycles, whereas that of Ni-ScSZ, conventional Ni-cermet anode was more than 20%. The STEM-EDX micrographs of the optimized anode are shown in Fig. 3, showing that catalytic Ni nanoparticles were supported on the LST-GDC composite frameworks in highly dispersed manner. Anode degradation mechanisms during cycle durability test suggested from these results are shown in Fig. 4. In the conventional Ni-cermet anodes, Ni grains increase in size with Red-Ox cycling and then its electron conducting framework is broken which deteriorates cell performance. On the other hand, in the best impregnated Ni-cermet anodes, Ni nanoparticles loaded on the LST –GDC composite anodes are difficult to aggregate during Red-Ox cycling. Consequently, the stable electrode frameworks exhibit negligible degradation. References 1. M.Hanasaki, C.Uryu, T.Daio, T.Kawabata, Y.Tachikawa, S.M.Lyth, Y.Shiratori, S.Taniguchi and K.Sasaki, J.Eletrochem.Soc. 161 (9) F850-860 (2014). 2. X. Shen, K. Sasaki, ECS Trans., 68(1), 1447-1453 (2015). Figure 1