Constructing an expeditious and durable composite as an air electrode of solid oxide cells through synergistic phase transformation and phase segregation engineering

Constructing an expeditious and durable composite as an air electrode of solid oxide cells through synergistic phase transformation and phase segregation engineering

The sluggish catalytic activity of iron-rich perovskite-based air electrodes at low temperatures (< 650 °C) is a common problem faced by solid oxide cells (SOCs). Herein, an expeditious and durable iron-rich, multifunctional, composite material is reported as an outstanding air electrode for SOCs. Such a composite consists of a dominant cubic single perovskite (SP) phase, SrFe1-x(Ta,Nb)xO3−δ, and a minor oxygen vacancy-rich double perovskite (DP) phase, Sr2FeNbO6−δ. The incorporation of pentavalent Ta and Nb effectively inhibits the formation of tetragonal SP and induces phase transformation to a cubic SP with high symmetry, while the in-situ separated DP phase synergistically boosts the performance of oxygen activation. Such multiple benefits result in the generation of an oxygen-ion conductor-based solid oxide fuel cell (O-SOFC) with the developed composite electrode that yields a superb maximum power density (Pmax) of 1259 mW cm−2 at 600 °C, ∼ 2.1 times that of an O-SOFC with SrFeO3−δ parent electrode (595 mW cm−2). A reversible protonic ceramic cell (R-PCC) with such composite air electrode delivers a remarkable electrochemical performance, e.g., a Pmax of 844 mW cm−2 and an electrolysis current density of −957 mA cm−2 @ 1.3 V at 650 °C. More attractively, the resulting cell exhibits an outstanding operating endurance of 500 hours in fuel cell mode and 210 hours in cycle mode (i.e., alternating between fuel cell and electrolysis cell modes).

© YEAR. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/