One breakthrough in developing highly efficient air electrodes for reversible protonic ceramic electrochemical cells (R-PCECs) is optimizing the sluggish oxygen reduction and water oxidation reactions. Here, we present a novel composite material with a nominal formula of high-entropy Ce_0.2Ba_0.2Sr_0.2La_0.2Ca_0.2CoO_3−δ (CBSLCC) that spontaneously self-assembles to three-phase electrocatalysts composed of deficient Ce_0.2−yBa_0.2Sr_0.2−xLa_0.2−xCa_0.2CoO_3−δ (CD-CBSLCC), CeO₂, and La_0.5Sr_0.5CoO_3−δ (LSC). Mechanistic studies corroborate that oxygen reduction may occur on entire air electrode surfaces, followed by water formation preferentially at or near CD-CBSLCC. The CeO₂ phase could provide or consume protons to facilitate the oxygen evolution/reduction kinetics in R-PCECs. The developed electrodes demonstrate a record-high electrochemical performance in dual modes of fuel cells and electrolysis cells, delivering a peak power density of 1.66 W cm⁻² at 600 °C and a current density of −1.76 A cm⁻² at 1.3 V and 600 °C. Excellent operational stabilities of the fuel cell (200 h at 600 °C), electrolysis cell (200 h at 600 °C), and reversible cycling (548 h at 550 °C) provide a promising and reliable step towards realizing the commercialization of R-PCECs.

中文翻译：

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复合空气电极的相分离释放了可逆质子陶瓷电化学电池的高性能


开发用于可逆质子陶瓷电化学电池（R-PCEC）的高效空气电极的一项突破是优化缓慢的氧还原和水氧化反应。在这里，我们提出了一种新型复合材料，其名义分子式为高熵 Ce _0.2 Ba _0.2 Sr _0.2 La _0.2 Ca < b4> CoO _3−δ (CBSLCC)，自发自组装成由缺陷 Ce _0.2−y Ba _0.2 Sr _0.2−x La _0.2−x Ca _0.2 CoO _3−δ (CD-CBSLCC)、CeO ₂ 和 La _0.5 CoO _3−δ (LSC)。机理研究证实，氧还原可能发生在整个空气电极表面，随后优先在 CD-CBSLCC 处或附近形成水。 CeO ₂ 相可以提供或消耗质子以促进 R-PCEC 中的析氧/还原动力学。所开发的电极在燃料电池和电解电池的双模式中表现出创纪录的电化学性能，在600°C下提供1.66 W cm ⁻² 的峰值功率密度和-1.76 A cm < b18> 在 1.3 V 和 600 °C 下。燃料电池（600 °C 下 200 小时）、电解池（600 °C 下 200 小时）和可逆循环（550 °C 下 548 小时）出色的运行稳定性为实现 R 商业化提供了有前景且可靠的一步-PCEC。