B-site nickel tuned high active Sr and Co-free Ba0.8Ca0.2Fe0.8Ni0.2O3-δ air electrode for reversible solid oxide cells

Abstract

Reversible solid oxide cells (RSOCs) have aroused wide concern as a promising technology in conversion between chemical energy and electrical power. However, the double conducting (O2−/e−) air electrode with high electrocatalytic activity and thermomechanical stability keeps a significant challenge for practical application. Herein, a perovskite Ba0.8Ca0.2Fe0.8Ni0.2O3-δ (BCFNi) oxide is synthesized and used as the air electrode material, which is experimentally and theoretically demonstrated to have excellent oxygen reduction/evolution reactions (ORR/OER) activity. The density functional theory (DFT) calculations indicate that BCFNi oxide accelerates the oxygen desorption/desorption, thus promoting the OER/ORR kinetics. The cell with BCFNi air electrode achieves a peak power density of 1.29 W cm−2 in the fuel cell (FC) mode and an electrolysis current density of 1.47 A cm−2 with 50 % H2O-H2 at 1.3 V applied voltage in the electrolysis cell (EC) mode at 800 °C. Moreover, it maintains favorable durability of 225 h in the FC, reversible, and EC modes at 750 °C, respectively. The results suggest that the Ni doping in B-site of perovskite oxide is beneficial to improve the ORR/OER activity and BCFNi material has great potential as an air electrode for RSOCs.