Preserving a Kinetically-Metastable Nanophase by Limited Calcination for High-Performance Protonic Ceramic Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 42351335.
- Also identified by DOI 10.1002/adma.73819.
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Abstract
Sluggish oxygen reduction/evolution reactions (ORR/OER) at the air electrode critically limit the efficiency of reversible protonic ceramic cells (r-PCCs), yet conventional high-temperature calcination of the air electrode leads to undesired surface passivation, while low-temperature calcination leads to insufficient crystallization, both of which severely impair electrocatalytic activity. Here we employ a thermally-limited calcination process to kinetically retain a nanophase in the air electrode that only forms at a selected calcination temperature (termed "metastable"), thereby forming rich heterointerfaces for active ORR/OER. Specifically, controlled calcination temperature induces selective Ce incorporation into the host lattice of Ba(Co,Fe,Y)O<sub>3-δ</sub> while preserving the metastable BaCeO<sub>3</sub>-related nanophase. This nanostructure enriches oxygen-vacancy-related defects, accelerates surface exchange and bulk diffusion, promotes proton incorporation, and improves thermomechanical compatibility with the electrolyte. The as-developed electrode (BaCo<sub>0.6</sub>Fe<sub>0.2</sub>Y<sub>0.1</sub>Ce<sub>0.1</sub>O<sub>3-δ</sub>-BaCeO<sub>3</sub>) exhibits a low resistance of 0.38 Ω cm<sup>2</sup> at 550°C. Single cells with this electrode deliver a high peak power density of 1.44 W cm<sup>-2</sup> at 650°C and an electrolysis current density of -2.47 A cm<sup>-2</sup> at 1.3 V. These findings establish a promising strategy of thermally-limited calcination for designing high-performance reversible protonic ceramic cells.