High-entropy engineering tuning electrochemical activity and stability of a layered double perovskite oxygen electrode for high-performance protonic ceramic cells

Abstract

Developing robust, highly active oxygen electrodes for protonic ceramic cells (PCCs) represents a crucial step in the pursuit for the efficient production of hydrogen and electricity at reduced temperatures. Here, we leverage a high-entropy design to introduce a multicomponent A-site double perovskite, Pr_0.2La_0.2Sm_0.2Nd_0.2Gd_0.2BaCo₂O_5+δ (PBC-HE), as a high performance oxygen electrode for PCCs. Compared with the parent PrBaCo₂O_5+δ (PBC), PBC-HE exhibits superior proton uptake ability, a markedly higher oxygen vacancy concentration, and enhanced thermal stability. The electrode reaction kinetics is significantly accelerated. The PBC-HE electrode achieves a low polarization resistance of 0.064 Ω cm² at 700 °C and, when integrated into a BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ-based cell, delivers a high peak power density of 1.01 W cm⁻² in fuel-cell mode. Under 10 vol% H₂O at the oxygen electrode, it sustains a current density of 1.74 A cm⁻² at 1.3 V in electrolysis cell mode at 700 °C. PBC-HE also exhibits remarkable durability, operating stably for 140 h in fuel cell mode and 100 h in electrolysis cell mode. These finding demonstrate that the rationally designed high-entropy double perovskite holds a great promise as high performance oxygen electrodes for application in PCCs.