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Lookup NU author(s): Dr Stevin Pramana
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© The Royal Society of Chemistry.La2NiO4+δ (LNO214) is a potential intermediate temperature solid oxide fuel cell (IT-SOFC) cathode material which belongs to the Ruddlesden-Popper (RP) structure series An+1BnO3n+1. There is interest in this material as it offers a way to avoid Sr segregation and associated degradation, as LNO214 can take in oxygen interstitials and become catalytically active without A-site doping. While the bulk ionic conduction mechanisms are well studied, its surface structure and chemistry are still a matter of debate. Recent experimental studies (both with and without dopants) reveal that it has a La-terminated surface and a highly Ni deficient surface layer. These results disagree with previous computer simulations, and undermine the conventional explanation for the oxygen reduction process at the surface. In this work we evaluate the thermodynamic stability of La2NiO4+δ at IT-SOFC operation temperatures. We find that the decomposition of La2NiO4+δ to produce La2O3 and higher order RP phases is indeed thermodynamically favourable. A hypothesis for the formation mechanism of the La-terminated and Ni deficient surface based on partial decomposition and surface passivation is proposed and evaluated.
Author(s): Wu J, Pramana SS, Skinner SJ, Kilner JA, Horsfield AP
Publication type: Article
Publication status: Published
Journal: Journal of Materials Chemistry A
Print publication date: 21/12/2015
Online publication date: 16/10/2015
Acceptance date: 13/10/2015
Date deposited: 06/04/2017
ISSN (print): 2050-7488
ISSN (electronic): 2050-7496
Publisher: Royal Society of Chemistry
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