High-entropy-induced CoO6 octahedral distortion for boosted oxygen evolution reaction at high temperature

Abstract

Modulating the distortion of BO6 octahedral plays a pivotal role in determining the physiochemical properties and electrocatalytic performance of the perovskite oxide (ABO3-δ). By tailoring the degree of octahedral tilting and bond angles, it could finely tune the electronic structure, oxygen vacancy formation, and ionic transport pathways within the perovskite lattice. Herein, we propose an efficient strategy to tune the BO6 (CoO6) octahedral distortion by the A-site high-entropy engineering in the Nd0.2Pr0.2La0.2Ba0.2Sr0.2CoO3-δ anode with the average Co-O-Co angle decreasing from 175° to 149°. Exsitu and in situ characterizations and density functional theory calculations reveal that the high-entropy-induced CoO6 octahedral distortion could shift the O 2p band center of the perovskite anode towards the Fermi level, and consequently activate the lattice oxygen and accelerate the transport of oxygen ions. Electrochemically, the CoO6-distorted Nd0.2Pr0.2La0.2Ba0.2Sr0.2CoO3-δ anode exhibits promoted high-temperature oxygen evolution reaction (OER) performance in solid oxide electrolysis cells (SOECs), with a high current density of 3.96 A·cm-2 at 1.5 V at 800 °C and stability for up to 600 hours, which is superior to most reported anode materials. This work discloses the impact of CoO6 octahedral distortion on high-temperature OER performance at atomic scale, and proposes an effective strategy for designing efficient and durable anodes of SOECs.