Recent developments in Ruddlesden-Popper nickelate systems for solid oxide fuel cell cathodes

Motivated by recent work on the Ruddlesden-Popper material, La2NiO4+delta; which was shown to be a superior oxide-ion conductor than conventional solid-oxide fuel cell cathode perovskite materials, we undertook A- and B-site doping studies of the Ruddlesden-Popper nickelate series in an attempt to identify other candidates for cathode application. In this paper, we summarize our most significant results for the La2Ni1-xCoxO4+delta and La2-ySmy NiO4+delta systems and more recently, the higher-order Ruddlesden-Popper phases La(n+1)Ni(n)O3(n+1) (n = 2 and 3), which show greater promise as cathode materials than the n = 1 compositions.