SOLID OXIDE FUEL CELLS: RECENT SCIENTIFIC AND TECHNOLOGICAL ADVANCEMENTS Improved Tolerance of Lanthanum Nickelate (La 2 NiO 4+d ) Cathodes to Chromium Poisoning Under Current Load in Solid Oxide Fuel Cells YIWEN GONG, 1,3 RUOFAN WANG, 1,4 JANE BANNER, 1,5 SOUMENDRA N. BASU, 1,2,6 UDAY B. PAL, 1,2,7 and SRIKANTH GOPALAN 1,2,8 1.—Division of Materials Science and Engineering, Boston University, 15 St. Mary’s St, Boston, MA 02215, USA. 2.—Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA 02215, USA. 3.—e-mail: yiwen@bu.edu. 4.—e-mail: wangrf@bu.edu. 5.—e-mai- l: jbanner@bu.edu. 6.—e-mail: basu@bu.edu. 7.—e-mail: upal@bu.edu. 8.—e-mail: sgopalan@- bu.edu Lanthanum nickelate, La 2 NiO 4+d (LNO), is studied as a cathode material for use in solid oxide fuel cells with the objective of mitigating chromium poi- soning. Under current load, both electrochemical and chemical reactions cause chromium poisoning, and high current density and humidity accelerate the poisoning. However, compared with a standard strontium-doped lanthanum manganite cathode, the LNO cathode has a much higher tolerance for chro- mium poisoning. This can be ascribed to a greatly reduced chromium depo- sition in LNO. INTRODUCTION Intermediate temperature (600–800°C) solid oxide fuel cells (IT-SOFCs) are considered as poten- tial energy conversion systems because of their high efficiency and low emissions. 1–3 Among the many metal alloys, ferritic stainless steels are the most promising interconnects at intermediate tempera- tures due to their high oxidation resistance and great thermal compatibility with other SOFC com- ponents. Vapor phase chromium species formed from the ferritic stainless steel interconnects and depositing in the triple-phase boundaries of the cathode 4–8 lead to cell performance deterioration. Mitigation strategies that combine protective coatings on metallic interconnects 9–12 and chro- mium-tolerant cathodes of the type investigated in this study will offer the best long-term solution to address chromium poisoning. It has been reported that Sr- and Mn-containing cathode materials, such as (La,Sr)(Co,Fe)O 3 (LSCF) and (La,Sr)MnO 3 (LSM), are sensitive to Cr poison- ing. The main compounds formed through reaction with Cr-vapor phase species and the aforemen- tioned cathodes, leading to degradation, are SrCrO 4 , Cr 2 O 3 and (Cr,Mn) 3 O 4 . 13–15 Thus, new Sr and Mn- free cathodes are desirable. Komatsu et al. 16 inves- tigated the effect of chromium poisoning on per- ovskite-structured LaNi 0.6 Fe 0.4 O 3 (LNF) as a cathode material and found that the cathodic over- potential of LNF was not a function of the presence of chromium. Rare earth nickelates, with the Ln 2 NiO 4+d (Ln = La, Nd, Sm, Pr, etc.) formula, with alternating blocks of perovskite LnNiO 3 and rock-salt, Ln 2 O 2 layers are known to be good SOFC cathodes. 17 This layered structure can accommodate excess lattice oxygen in interstitial sites, resulting in high oxygen ion diffusivities and oxygen surface exchange coef- ficients. 18,19 Laberty et al. 20 showed that power density of 2.2 W/cm 2 can be achieved using LNO This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial pro- duct, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, rec- ommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed therein do not nec- essarily state or reflect those of the United States Government or any agency thereof. JOM, Vol. 71, No. 11, 2019 https://doi.org/10.1007/s11837-019-03724-0 Ó 2019 The Minerals, Metals & Materials Society 3848 (Published online August 20, 2019)