Effect of Nature of the Ceramic Component of the Composite Electrodes Based on La1.7Ca(Sr)0.3NiO4+δ on Their Electrochemical Performance

The development of a cathode that is stable against CO₂ present in the atmosphere still remains a challenge. Over the past ten years layered perovskite La₂NiO_4±δ has been the subject of careful research as far as also concerns their potential use as cathodes in electrochemical devices. So far as La₂NiO_4±δ is a p-type conductor, appropriate acceptor doping on A-site could improve the electronic conductivity by generating extra electron holes for charge compensation. Experimental results reveal that the electronic conductivity does indeed increase with a certain amount of Sr or Ca-doping. However, the substitution of La by alkali-earth elements deteriorates its electrochemical activity due to a decrease in the sub-stoichiometric oxygen amount in the structure and ionic component of conductivity [1]. One way to increase ionic conductivity is development of composite electrodes with ionic conductor as a second component, usually CeO₂-based electrolyte [2]. The composite electrodes with proton-conducting electrolyte, especially in case when such electrodes are proposed to be used in contact with this electrolyte, could provide more extended area of electrochemical reaction.

     The actual work focuses on the electrochemical performance of the La_1.7Ca(Sr)_0.3NiO₄-based composite cathode materials with Ce_0.8Sm_0.2O_1.9 (SDC) and BaCe_0.89Gd_0.1Cu_0.01O₃ (BCGC) ceramic component (in wight ratio 1:1) which were applied as a functional layer in two-layered electrodes with 98 wt.% LаNi_0.6Fe_0.4O₃ + 2 wt.% CuO LаNi_0.6Fe_0.4O₃ and 99.4 wt. % La_0.6Sr_0.4MnO₃ + 0.6 wt.% CuO as a collector layer. Studies by impedance spectroscopy were performed in contact with BCGC and BaCe_0.5Zr_0.3Y_0.2O₃ + 1 wt.% CuO (BCZY) proton-conducting electrolytes in comparison with traditionally used 50 wt.% La_0.6Sr_0.4Fe_0.8Co_0.2O₃ + 50 wt.% SDC and 50 wt.% La_0.75Sr_0.2MnO₃ + 50 wt.% SSZ composite electrodes.

Keywords: La_1.7Ca_0.3NiO₄, cathode, electronic conductivity, proton-conducting electrolyte

Acknowledgments

The authors are grateful for the financial support to: the Ministry of Education and Science of the Russian Federation (Mega-grand contract no. 14.Z50.31.0001), the Russian Foundation for Basic Research (grants no. 13-03-00065, 14-03-00414) and the Russian Foundation for Basic Research (grants no. 13-03 96098 and 14-03-00414).

 References

[1] E.Yu. Pikalova, N.M. Bogdanovich, A.А. Kolchugin, D.A. Osinkin, D.I. Bronin, Electrical and electrochemical properties of La₂NiO_4+δ-based cathodes in contact with Ce_0.8Sm_0.2O_2-δelectrolyte, accepted in Procedia Engineering

[2] B.L. Kuzin, N.M. Bogdanovich, D.I. Bronin et al, Elecrochemical Properties of Cathodes Made of (La,Sr)(Fe,Co)O₃Containing Admixtures of Nanoparticles of Cupric Oxide and Intended for Fuel Cells with A Solid Electrolyte Based on Ceric Oxide, Rus. J. Electrochem. 43 (2007) 920.