A Superior Catalytic Air Electrode with Temperature-Induced Exsolution toward Protonic Ceramic Cells

Abstract

Protonic ceramic cells merit extensive exploration, attributed to their innate capabilities for potent and environmentally benign energy conversion. In this work, a temperatureinduced exsolution methodology to synthesize SrCo 0.5 Nb 0.5 O 3−δ (SCN) nanoparticles (NPs) with notably elevated activity on the surface of PrSrCo 1.8 Nb 0.2 O 6−δ (PSCN) is proposed, directly addressing the extant challenge of restrained catalytic activity prevalent in air electrode materials. In situ assessments reveal that SCN NPs commence exsolution from the matrix at temperatures surpassing 900 °C during straightforward calcination processes and maintain stability throughout annealing. Notably, the resultant SCN−PSCN interface facilitates vapor adsorption and protonation processes, which are poised to enhance surface reaction kinetics pertaining to the proton-involved oxygen reduction and evolution reaction (P-ORR and P-OER). A fuel-electrode-supported protonic ceramic cell leveraging SCN−PSCN as the air electrode manifests compelling performance, attaining a peak power density of 1.30 W•cm −2 in the fuel cell modality and a current density of 1.91 A•cm −2 at 1.3 V in the electrolysis mode, recorded at 650 °C. Furthermore, density functional theory calculations validate that the introduction of SCN NPs onto the PSCN surface conspicuously accelerates electrode reaction rates correlated with P-ORR and P-OER, by significantly mitigating energy barriers associated with surface oxygen and vapor dissociation.

An active and durable air electrode with self-generated nanoparticles decorated on the surface for reversible oxygen-ionic ceramic electrochemical cells

“…Over 900 °C, the slight increase may be related to the transition of SCN–PSCN crystal structure. 49 In particular, the weight loss rate rises dramatically above 800 °C, producing a significant amount of lattice oxygen loss and therefore a significant quantity of oxygen vacancies. 4 Shown in Fig.…”

A Highly Active and Robust Air Electrode for Reversible Protonic Ceramic Cells: Advanced Performance Achieved by Low-Lewis-Acid-Strength Cation Doping Strategy

“…Regulating the energy composition by developing a clean power system is a beneficial way to alleviate the pressure on the environment. − Among all the renewable energy sources, reversible protonic ceramic cell (RPCC) technology advances discontinuous energy systems (solar, wind, and tides) by higher functionality and reliability from a long-term perspective. In the dual-mode operation, electricity or H 2 can be generated selectively in the reversible processes. , Evolved from the traditional oxygen ion conductive cells, the proton conductive RPCCs show the significant superiority of structural robustness and low maintenance costs owing to the lowered operation temperature. , With the progressions of the RPCC technology, the ever-lowering working temperature enables the flexible selection of constituent materials, while also bringing new challenges for the air electrode. , …”

“…For BKCX, less time is needed to reach the adsorption saturation compared to the BCX, further verifying the positive effect of K-doping on hydroxylation reactive activity. , As for the O speciation, two samples were subjected to the XPS analysis as shown in Figure e,f. The O 1s spectra could be deconvoluted into four peaks, including lattice oxygen species (≈528.8 eV, O lat ), highly oxidative species (≈529.4 eV, O – /O 2– ), the hydroxyl groups or the oxygen adsorbed on the surface (≈531.4 eV, O abs ), and the oxygen in chemisorbed H 2 O or CO 3 2– (≈533.7 eV, O H ). , The ratio of O – /O 2– to O lat serves as an indicator for the oxygen vacancies content; the ratios of BKCX and BCX are 2.68 and 1.81, respectively (Figure S3). , The introduction of K as a dopant could potentially enhance the oxygen vacancy content .…”