Influence of A-site Deficiency and Ni/Co Ratio in B-site on Electrochemical Performance of (La0.25Sr0,25Ca0.45)yTi0.95Ni0.05-xCoxO3- d Anode

Abstract

La 0.25 Sr 0.25 Ca 0.45 TiO 3 - d (LSCT) is a perovskite (ABO 3 ) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell [1]. This material owing high conductivity, robustness in hydrocarbon fuels and significant amount of attention has been paid to improve the electrochemical activity [1, 2]. Doping of B-site with some d-metal cation (Ni, Co, Mn, V, Mo) has been demonstrated to improve the catalytic activity. One of the advantages of the MIEC conducting scaffold based electrodes is that the catalyst phase on the electrode surface can be kept to a minimum, usually less than 5 wt%, which minimizes any risks of physical damage during redox cycling [2]. In this work, Ni/Co ratio and deficiency of A-site, of (La 0.25 Sr 0.25 Ca 0.45 ) x Ti 0.95 Ni 0.05-y Co y O 3 - d were varied. Electrical as well as electrochemical performance and chemical composition of LSCTNC surface was monitored. The electrochemical measurements of symmetric cells during 100 h tests show that small stochiometric changes in A-site significantly influence the activity and initial degradation rate of the electrode. The chemical and structural changes of the material surface have a key role on the electrochemical performance of the electrode [3]. The electrode materials were analysed using XRD, TOF SIMS and electrochemical methods. XRD and TOF SIMS results for studied electrode powders showed significant dependence of the lattice parameters and electrode surface composition on the perovskite elemental composition. The results from impedance spectroscopy (measured at temperatures from 973 to 1123 K in H 2 environment, at OCV) demonstrate a significant influence of the A-site deficiency and B-site composition on the electrochemical properties of studied electrodes. Robert Price, Mark Cassidy, Jan G. Grolig, Gino Longo, Ueli Weissen, Andreas Mai, John T. S. Irvine, Advanced Energy Materials, 11, 1 (2021). Paul A. Connor, Xiangling Yue, Cristian D. Savaniu, Robert Price, Georgios Triantafyllou, Mark Cassidy, Gwilherm Kerherve, David J. Payne, Robert C. Maher, Lesley F. Cohen, Rumen I. Tomov, Bartek A. Glowacki, Ramachandran Vasant Kumar, John T. S. Irvine, Advanced Energy Materials, 8, 1 (2018). Ove Korjus, Priit Möller, Kuno Kooser, Tanel Käämbre, Olga Volobujeva, Jaak Nerut, Sander Kotkas, Enn Lust, Gunnar Nurk, Journal of Power Sources, 494, 1 (2021).