Novel materials based on Ruddlesden–Popper phases for solid oxide fuel cells and oxygen separation membranes: Fundamentals of oxygen transport

Abstract

In the field of modern hydrogen energy, obtaining pure hydrogen and syngas and then being able to use them for green energy production are significant problems. Developing solid oxide fuel cells (SOFC) and catalytic membranes for oxygen separation as well as materials for these devices is one of the most likely ways to solve these problems. First-order Ruddlesden–Popper phases are important materials for such devices. In this review, fundamentals of developing such materials for SOFC cathodes and oxygen separation membranes’ permselective layers based on research of their oxygen mobility and surface reactivity are presented. For Ruddlesden–Popper phases Ln2−xMxNiO4+δ, Ln2−xCaxNi1−yCuyO4+δ, and Ln2−xLn’xNiO4+δ (Ln = La, Pr, Nd; Ln’ = Pr, Nd, Sm, Eu, Gd; M = Ca, Sr, Ba) a high oxygen mobility is shown (D* ~ 10−7 cm2/s at 700 °C) by isotope exchange of oxygen techniques, being provided by the cooperative mechanism of oxygen migration involving both regular and highly-mobile interstitial oxygen. After optimization of composition and nanodomain structure of these materials, as cathodes of SOFC they provided a high power density, while for asymmetric supported oxygen separation membranes – a high oxygen permeability. Hence, the application of mixed ionic-electronic materials with high oxygen mobility and surface reactivity and optimized structural, morphological and textural properties is a promising approach in the design of SOFC cathodes and oxygen separation membranes