Youcheng Xiao,Di Bao,Zhen Wang,Yaowen Wang,Tianmin He
Using symmetrical electrodes with the same material compositions can simplify the manufacturing process, reduce cost, and enhance the stability and reliability of solid oxide cells. Herein, we report for the first time the potential application of the La 0.3 Sr 0.7 Fe 0.7 Cr 0.3 O 3-δ (LSFC) perovskite as a symmetrical electrode for reversible protonic ceramic cells (RPCCs). The LSFC exhibits robust chemical stability in oxidizing and reducing environments and favorable chemical compatibility with BaZr 0.4 Ce 0.4 Y 0.15 Zn 0.05 O 3-δ electrolyte below 950 °C. Using LSFC as a symmetrical electrode, the electrolyte-supported RPCC delivers a maximum power density of 76 mW cm −2 in fuel cell (FC) mode at 700 °C, and a maximum current density of 30 mA cm −2 in electrolysis cell (EC) mode at 1.5 V; no significant degradation is shown under both FC and EC modes during 100 h continuous operation. The LSFC shows remarkably low polarization resistances (R p ) of 0.06 and 0.07 Ω cm 2 at 700 °C in dry and wet air, which allows it to be used directly as an air electrode; while it is 3.46 Ω cm 2 at 700 °C in 5%H 2 /Ar, which needs to improve its catalytic activity to enhance the overall performance of symmetrical electrode. These results allow us to propose a feasible strategy for applying symmetrical electrodes in RPCCs.
Reversible protonic ceramic cells (R-PCCs) have been in the spotlight as prominent electrochemical devices for green hydrogen production and utilization. The design of efficient air electrodes is critical for enhancing cell performances, requiring high hydration ability, excellent catalytic activities, and appropriate thermal expansion coefficients (TEC). Herein, novel high-entropy oxides La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Me 0.2 )O 3– δ (Me = Al, Mn, Cr) featuring five cations at B-site of ABO 3 perovskite are presented. La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Cr 0.2 )O 3– δ (LCCFN-Cr) catalyst exhibits the best proton incorporation ability and catalytic activities among three oxides, concluded by analyzing the oxygen vacancy concentration and the chemical bond information. Moreover, the high-entropy effect at B-site reduced the TEC of this Co-contained oxide to a modest extent through large-ratio substitution of Co by other cations. When applied as an air electrode, the BaZr 0.6 Ce 0.2 Y 0.1 Yb 0.1 O 3– δ electrolyte-based R-PCCs yielded a high current density of 2.14 A cm −2 and a peak power density of 0.60 W cm −2 , with an extremely low polarization resistance of 0.05 Ω cm 2 at 650 °C. These findings not only provide a novel air electrode for R-PCCs, but also demonstrate a pathway to design effective oxide catalysts for other energy conversion devices by integrating the advantages of Co and high-entropy effect.
Ao Hu,Chenghao Yang,Yitong Li,Kaisheng Xia,Yunfeng Tian,Jian Pu,Bo Chi
Reversible proton ceramic cells (R-PCCs) offer a transformative solution for dual functionality in power generation and energy storage. However, their potential is currently obstacles by the lack of high-performance air electrodes combining high electrocatalytic activity with durability. Here, an innovative air electrode composed of high-entropy driven self-assembled xNiO-Pr 0.2 La 0.2 Ba 0.2 Sr 0.2 Ca 0.2 Fe 0.8 Ni 0.2−x O 3−δ (N-XFN) composites is presented, which result from the unique lattice distortion effects inherent in high-entropy perovskites. The experimental results coupled with density functional theory (DFT) calculations verify that the lattice distortion at the high-entropy A-site significantly induces NiO nanoparticles exsolved from the B-site, promoting the formation of a biphasic composite structure that dramatically increases the electrochemical active sites. Remarkably, R-PCCs using the N-XFN composite air electrode achieve an impressive peak power density of 1.30 W cm −2 in fuel cell mode and a current density of -2.52 A cm −2 at 1.3 V in electrolysis mode at 650 °C. In addition, the cells show excellent stability with reversibility over 830 h, including 500 h in electrolysis mode and 330 h in reversible operation at 650 °C. This research provides important insights into the design of high-entropy perovskites, paving the way for advanced R-PCCs technology.
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