High-entropy materials are attracting ever-increasing
concern for
their unique structural features and unprecedented potential applications.
In this study, we design and successfully prepared single-phase high-entropy
perovskite oxide (HEPO) BaSn0.16Zr0.24Ce0.35Y0.1Yb0.1Dy0.05O3−δ (BSZCYYbD) to use as a new class of proton conductor, which is first
applied to protonic ceramic fuel cells (PCFCs) below 600 °C.
The BSZCYYbD exhibits excellent chemical and structural stability,
high densification, and mechanical properties. The protonic conduction
in BSZCYYbD is proved by the proton-conductor isotope effect and hydration
effect. The protonic conductivity of BSZCYYbD is the highest ever
reached in the high-entropy proton conductors, which is 8.3 mS cm–1 in humidified air (3% H2O) at 600 °C.
An anode-based PCFC with BSZCYYbD electrolyte (∼45 μm)
demonstrates a favorable output of 318 mW cm–2 at
600 °C. Our study offers a strategy for the design of superior
proton-conducting electrolytes based on HEPOs, which hold promise
for diverse electrochemical applications.
BaCeO 3 -based proton conductors have comparatively high-proton conductivity, but the low chemical stability and high sintering temperature seriously hinder their practical applications in protonic ceramic fuel cells. Herein, we demonstrate that this limitation can be conciliated by using a triple-doping strategy in a BaZr 0.1 Ce 0.7 Y 0.2 O 3−δ (BZCY) electrolyte, where the triply doped BaCe 0.7 Sn 0.1 Dy 0.15 Cu 0.05 O 3−δ (BCSDCu) exhibits better chemical stability and conductivity and lower sintering temperature compared with the pristine BZCY. The phase-pure BCSDCu can be obtained at the sintering temperature of 1100 °C prepared by solid-state reaction. The dense BCSDCu (>95%) is achieved at 1350 °C, which is significantly lower than the 1550 °C of BZCY. The BCSDCu presents competitive proton conductivity of 13.6 mS cm −1 under a moist H 2 atmosphere at 600 °C. The anode-supported single cell with the BCSDCu (≈40 μm) as the electrolyte reaches the highest power density of 390 mW cm −2 at 600 °C. On the basis of the distribution of relaxation time analysis, we not only distinguish the contribution of grain and grain-boundary conductivities but also identify the rate-determining step of the single-cell performance. The protonic conductivities, mechanical properties, and impurity clean parts induced by grain size effects are discussed for the BCSDCu proton conductor.
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