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

Abstract

Motivated by recent work on the Ruddlesden–Popper material, ${\hbox{La}}_{2} {\hbox{NiO}}_{{4 + \delta }} ,$ 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 ${\hbox{La}}_{{\text{2}}} {\hbox{Ni}}_{{1 - x}} {\hbox{Co}}_{x} {\hbox{O}}_{{4 + \delta }}$and ${\hbox{La}}_{{2 - y}} {\hbox{Sm}}_{y} {\hbox{NiO}}_{{4 + \delta }}$systems and more recently, the higher-order Ruddlesden–Popper phases La _n+1Ni _n O_3n+1 (n=2 and 3), which show greater promise as cathode materials than the n=1 compositions.