It has been found in our previous study that La 0.9 Ca 0.1 Fe 0.9 Nb 0.1 O 3-δ -Sm 0.2 Ce 0.8 O 1.9 (LCFNb-SDC) anode shows high catalytic activity and stability for solid oxide fuel cells (SOFCs) under H 2 and CO atmospheres. In this study, LCFNb-SDC is further tuned into a promising anode for direct methane SOFCs through surface modification with Ni. The LCFNb, SDC and Ni materials are found to be thermal-mechanically and chemically compatible with each other up to 850 °C. Although LCFNb-SDC anode shows poor catalytic activity for methane oxidation , further modification of such anode with a small amount of Ni particles significantly improves the cell performance in CH 4 . The maximal power densities of 1031 and 729 mW cm −2 in H 2 and CH 4 have been achieved for the electrolyte supported SOFC with LCFNb-SDC-Ni|SSZ (Sc 0.2 Zr 0.8 O 2−δ )|LSM (La 0.8 Sr 0.2 MnO 3 ) configuration at 850 °C, respectively. Besides, the same cells also exhibit good stabilities in both H 2 (500 h) and CH 4 (100 h) with no obvious performance degradation and carbon deposition. Surface tuned LCFNb anode by impregnating SDC and a small amount of Ni is thus highly promising as an anode for direct methane SOFCs to deliver favorable performance with reasonable stability.
Limin Liu,Xiaoliang Zhou,Yong Wang,Si Li,Ran Yin,Pan Guo,Jinggeng Zhao,Xiaohong Zhao,Bin Li
In this paper, a novel composite La 0.9 Ca 0.1 Fe 0.9 Nb 0.1 O 3-δ /Sc 0.2 Zr 0.8 O 2−δ (LCFNb/ScSZ) is developed and investigated as a fuel electrode candidate for direct electrolyzing carbon dioxide (CO 2 ) in solid oxide electrolysis cells (SOECs). XRD patterns of LCFNb powder sintered in CO 2 at 850 °C for 10 h indicate that no secondary phases are found during the heat treatment and linear thermal expansion results prove that the LCFNb is compatible with ScSZ electrolyte used in this work. The electrolyser with porous LCFNb membrane cathode fabricated by infiltration method shows impressive electrochemical performance. The current density of 1.97 A/cm 2 at 2.0 V at 800 °C is obtained. The polarization resistance Rp of the SOEC decreases with the increase of the applied voltage between the electrodes. The obtained lowest Rp is as low as 0.113 Ω cm 2 at 2.0 V and this value is much lower than its many other perovskite and nickle-based counterparts. Besides, the LCFNb/ScSZ cathode shows excellent stability in pure CO 2 at different applied voltage, especially at 2.0 V. Furthermore, the LCFNb/ScSZ electrode exhibits the current efficiencies close to theoretical ones for CO 2 electrolysis, indicating that the LCFNb/ScSZ composite ceramic is an excellent cathode for zirconia-based high temperature electrolyser.
A novel La 0.9 Ca 0.1 Fe 0.9 Nb 0.1 O 3-δ (LCFNb) perovskite for solid oxide fuel cells (SOFCs) anode is prepared by means of the citrate-nitrate route and composited with Ce 0.8 Sm 0.2 O 1.9 (SDC) by impregnation method to form nano-scaled LCFNb/SDC anode catalytic layers. The single cells with LCFNb and LCFNb/SDC impregnated anodes both achieve relatively high power output with maximum power densities (MPDs) reaching up to 610, 823 mW·cm −2 in H 2 at 800 °C, respectively, presenting a high potential of LCFNb for use as SOFCs anode. The power outputs of the single cells with LCFNb/SDC composite anode in CO and syngas (CO H 2 mixture) are almost identical to that in H 2 at each testing temperature. This composite anode also presents excellent durability in both H 2 and CO for as long as 50 h, showing desirable anti-reduction and carbon deposition resistance abilities. Besides, the cell output is stable in 100 ppm H 2 S H 2 atmospheres for 20 h at a current density of 600 mA·cm −2 with negligible sulfur accumulation on the anode surface . Hence, a novel iron based perovskite LCFNb anode with remarkable cell performance, carbon deposition resistance and sulfur poisoning tolerance for SOFCs is successfully obtained.
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