Abstract
The development of oxygen electrodes with sufficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity, as well as good tolerance to contaminants, is crucial for promoting the commercialization of reversible solid oxide cells (Re-SOCs) technologies. Herein, we design and synthesize a medium-entropy oxygen electrode with a formula of Pr(0.5)Ba(0.2)Sr(0.2)Ca(0.1)CoO(3-δ) (ME-PBSCC). The abundant surface oxygen vacancy concentration, high electrical conductivity, rapid and stable oxygen exchange kinetics, and structural stability of the ME-PBSCC oxygen electrode ensure the efficient and poisoning-tolerant ORR/OER in ambient air and Cr-contaminated atmosphere. Specifically, Re-SOCs incorporating the PBSCC oxygen electrodes exhibit maximum power densities of 2.239 (in ambient air) and 1.859 W cm(-2) (in a Cr-contaminated air) at 750 (o)C in fuel cell (FC) mode, and current densities of 1.10 A cm(-2) at 1.3 V and 700 (o)C under 50% H(2)O (in a Cr-contaminated air) in electrolysis (EC) mode, demonstrating competitive performance for Re-SOCs. More importantly, the developed ME-PBSCC oxygen electrode has achieved the highly promising stable operation of Re-SOCs in FC, EC, and reversible modes in the presence of Cr contamination.