High-Entropy-Tailored d-p Orbital Hybridization for Enhanced Oxygen Reduction Reaction in Perovskite Air Electrodes of Solid Oxide Fuel Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 41913503.
- Also identified by DOI 10.1002/adma.72892.
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Abstract
Developing high-performance and durable air electrodes is crucial for the commercialization of medium-temperature solid oxide fuel cells (MT-SOFCs). Herein, we report a high-entropy Pr<sub>0.2</sub>Nd<sub>0.2</sub>Ba<sub>0.2</sub>Sr<sub>0.2</sub>Ca<sub>0.2</sub>CoO<sub>3-δ</sub> (PNBSCC) air electrode that demonstrates superior oxygen reduction reaction (ORR) catalytic activity and stability. The symmetrical cell with PNBSCC exhibits a polarization impedance (R<sub>p</sub>) of 0.048 Ω cm<sup>2</sup> at 650°C, significantly lower than the 0.196 Ω cm<sup>2</sup> of PrBaCo<sub>2</sub>O<sub>5 ± δ</sub> (PBC) counterpart. A single cell with the PNBSCC air electrode achieves an outstanding peak power density of 2.03 W cm<sup>-2</sup> at 800°C, representing a 153% improvement over that with PBC. Furthermore, the single cell maintains a voltage decay rate of only 0.047 mV h<sup>-1</sup> after 450 h of stable operation at 700°C. In situ high-temperature XRD and electrochemical impedance spectroscopy (EIS) reveal excellent CO<sub>2</sub> tolerance and structural stability of PNBSCC. Combined X-ray absorption spectroscopy and density functional theory calculations reveal weakened Co 3d-O 2p hybridization and reduced Co─O covalency in PNBSCC, which favors lattice-oxygen activation and oxygen-vacancy formation. The increased oxygen-vacancy population facilitates oxygen-ion transport, thereby accelerating ORR kinetics and improving cell performance.