Developing electrocatalysts for the oxygen evolution reaction (OER) is essential for enhancing the efficiency of electrochemical water electrolysis. Among potential candidates, certain metal oxides, such as BaSrCoFeO (BSCF), undergo structural transformations at their surface during OER operation, and the -formed active layer enhances their OER activities. However, it is challenging to quantitatively evaluate the time-variant electrochemically active surface area (ECSA) and inherent catalytic activity per surface area (area-specific activity) of the oxides. In this study, we utilize the 3-dimentional electrochemical impedance spectroscopy (3D EIS) technique to reveal the variations in the ECSA and area-specific activity of the perovskite oxides during OER operation in an alkaline solution. In BSCF, the diameter of instantaneous Nyquist plots decreases as the number of potential cycling in the OER potential range increases, contrasting with other perovskite oxides, such as LaSrCoFeO and LaCoO. The fitting results of the Nyquist plots demonstrate that in BSCF, the ECSA significantly increases while the area-specific activity drops to less than half of its initial value during OER operation. Consequently, enhanced OER activity of BSCF mainly attributed to the increased ECSA rather than area-specific activity. This study demonstrates the utility of 3D EIS for tracking the ECSA and the area-specific activity of electrocatalysts.

中文翻译：

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通过三维电化学阻抗谱追踪碱性溶液中钙钛矿氧化物析氧反应的活性行为


开发用于析氧反应（OER）的电催化剂对于提高电化学水电解的效率至关重要。在潜在的候选者中，某些金属氧化物，例如BaSrCoFeO (BSCF)，在OER操作期间其表面发生结构转变，并且形成的活性层增强了它们的OER活性。然而，定量评估氧化物随时间变化的电化学活性表面积（ECSA）和单位表面积固有的催化活性（面积比活性）具有挑战性。在这项研究中，我们利用三维电化学阻抗谱（3D EIS）技术来揭示钙钛矿氧化物在碱性溶液中OER操作期间ECSA和面积比活性的变化。在 BSCF 中，瞬时奈奎斯特图的直径随着 OER 电势范围内电势循环次数的增加而减小，这与其他钙钛矿氧化物（例如 LaSrCoFeO 和 LaCoO）形成鲜明对比。奈奎斯特图的拟合结果表明，在 BSCF 中，在 OER 操作期间，ECSA 显着增加，而区域比活性下降到其初始值的一半以下。因此，BSCF 的 OER 活动增强主要归因于 ECSA 的增加，而不是区域特定活动的增加。本研究展示了 3D EIS 在跟踪 ECSA 和电催化剂的特定区域活性方面的实用性。