Key Takeaways & Executive Findings
- •• HE-LSCF air electrode exhibits superior ORR activity with a low polarization resistance of 0.042 Ω·cm² at 700°C, significantly outperforming conventional LSCF. • Tubular R-SOCs with HE-LSCF achieve a high peak power density of 1.18 W·cm⁻² in fuel cell mode and a promising electrolysis current density of −0.52 A·cm⁻² at 1.5 V. • The high-entropy design effectively mitigates Sr segregation, enhancing structural stability and durability over 180 h of reversible cycling. • This work demonstrates that A-site high-entropy engineering is a viable strategy to boost both activity and robustness of perovskite air electrodes for R-SOCs.
Abstract
Developing highly active and stable air electrodes remains challenging for reversible solid oxide cells (R-SOCs). Herein, we report an A-site high-entropy engineered perovskite oxide, La0.2Pr0.2Nd0.2Ba0.2Sr0.2Co0.8Fe0.2O3−δ (HE-LSCF), and its electrocatalytic activity and stability property are systematically probed for tubular R-SOCs. The HE-LSCF air electrode exhibits excellent oxygen reduction reaction (ORR) activity with a low polarization resistance of 0.042 Ω·cm2 at 700°C, which is much lower than that of La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF), indicating the excellent catalytic activity of HE-LSCF. Meanwhile, the tubular R-SOCs with HE-LSCF shows a high peak power density of 1.18 W·cm−2 in the fuel cell mode and a promising electrolysis current density of −0.52 A·cm−2 at 1.5 V in the electrolysis mode with H2 (~10% H2O) atmosphere at 700°C. More importantly, the tubular R-SOCs with HE-LSCF shows favorable stability under 180 h reversible cycling test. Our results show the high-entropy design can significantly enhance the activity and robustness of LSCF electrode for tubular R-SOCs.
1. Introduction
Reversible solid oxide cell (R-SOC) is considered as an efficient energy conversion device that interconverts between chemical and electrical energy [1–3]. Excess intermittent renewable energy can be used for high-temperature electrolysis to generate hydrogen or carbon-based fuels in electrolysis cell (EC) mode, and efficiently convert the chemical energy into electricity in fuel cell (FC) mode, enabling peak shaving and valley filling of electrical energy [4–6]. Sluggish oxygen reduction (ORR) and oxygen evolution (OER) kinetics, coupled with the limited stability of the air electrode, are key constraints on R-SOC advancement [7–9]. Therefore, novel air materials with excellent activity and durability are particularly important for advancing the development of R-SOCs [10–13].
Although some perovskite-type material with mixed ion-electron conductors, such as Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) [14], SrCo0.9Nb0.1O3−δ (SCN) [15], and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF28) [16] have been recognized as effective air electrode materials for R-SOCs, owing to their superior catalytic activity and high electrical conductivity. These materials need enhancement as air electrodes for R-SOCs since Sr segregation over prolonged operation causes structural deterioration and catalyst deactivation [17–18]. For instance, Zhao et al. [19] conducted an in-depth study on the surface polarization behavior of a dense LSCF28 rod sample. It was demonstrated that the pristine LSCF28 surface was smooth, and nano and submicron particles were enriched in Sr after 96 h of heat treatment at 800°C in air, indicating that Sr was segregated from the LSCF28 structure.
Recently, high-entropy perovskite materials are highly regarded for their versatility in tuning material functionality in solid oxide fuel cells (SOFCs), electrocatalysis field, etc. [20–22]. In SOFC, some researchers have improved the disorder of perovskite oxides through multi-element doping and enhanced its catalytic activity of air electrode. On the one hand, a Ruddlesden–Popper-structured B-site high-entropy perovskite material (La1.4Sr0.6Co0.2Fe0.2Ni0.2Mn0.2Cu0.2O4±δ) has been reported to exhibit rapid ORR and OER kinetics as an air electrode, and it has been proved that high entropy strategies can effectively avoid Sr segregation [23]. On the other hand, researchers have engineered A-site of perovskite oxides to improve oxygen-ion conductivity and electrochemical performance in air electrodes, yielding notable results. Han et al. [24] explored a high perovskite oxide La0.2Pr0.2Nd0.2Sm0.2Gd0.2BaFe2O5+δ as air electrode with excellent electrochemical catalytic activity and stability in Cr vapor atmosphere. He et al. [25] proposed the Pr0.2Ba0.2Sr0.2La0.2Ca0.2CoO3−δ electrode with high performance and durability properties as air electrode. Meanwhile, a high-entropy perovskite (Pr1/6La1/6Nd1/6Ba1/6Sr1/6Ca1/6CoO3−δ) with six alkaline earth metals or rare earth metals was reported as the air electrode of proton solid oxide cell, showing the improved electrochemical performance and stability [26]. Therefore, incorporating additional metal cations into the perovskite oxide lattice is a promising strategy to enhance performance and stability.
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Shiyue Zhu, Tian Li, Ruoyu Li, Xiaoyong Lu, Yihan Ling, Dong Tian (2025). A high-entropy engineered perovskite oxide for efficient and stable LSCF-based air electrode of tubular reversible solid oxide cells. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3159-x
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Frequently Asked Questions
What is the main innovation of this paper?
The paper introduces an A-site high-entropy engineered perovskite oxide (HE-LSCF) as an air electrode for tubular reversible solid oxide cells, which significantly enhances electrocatalytic activity and stability compared to conventional LSCF.
How does the high-entropy design improve the performance of the air electrode?
The high-entropy design increases configurational entropy, which suppresses Sr segregation and enhances structural stability, while also improving oxygen reduction reaction activity and overall electrochemical performance.
What are the key performance metrics reported for HE-LSCF?
HE-LSCF exhibits a low polarization resistance of 0.042 Ω·cm² at 700°C, a peak power density of 1.18 W·cm⁻² in fuel cell mode, and an electrolysis current density of −0.52 A·cm⁻² at 1.5 V, with stable operation over 180 h of reversible cycling.
Why is stability important for reversible solid oxide cells?
Stability is crucial because air electrodes often suffer from Sr segregation and structural degradation during prolonged operation, which reduces performance and lifespan. The high-entropy approach mitigates these issues, ensuring long-term durability.
What is the significance of using tubular geometry in this study?
Tubular R-SOCs offer advantages such as higher mechanical strength, better thermal cycling resistance, and easier sealing compared to planar designs, making them promising for practical applications. The study demonstrates that HE-LSCF works effectively in this configuration.
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