Department of Material Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Argonne National Laboratory, Lemont, IL, 60439, USA.
Nat Commun. 2019 Mar 22;10(1):1346. doi: 10.1038/s41467-019-08674-4.
Reducing the working temperature of solid oxide fuel cells is critical to their increased commercialization but is inhibited by the slow oxygen exchange kinetics at the cathode, which limits the overall rate of the oxygen reduction reaction. We use ab initio methods to develop a quantitative elementary reaction model of oxygen exchange in a representative cathode material, LaSrCoO, and predict that under operating conditions the rate-limiting step for oxygen incorporation from O gas on the stable, (001)-SrO surface is lateral (surface) diffusion of O-adatoms and oxygen surface vacancies. We predict that a high vacancy concentration on the metastable CoO termination enables a vacancy-assisted O dissociation that is 10-10 times faster than the rate limiting step on the Sr-rich (La,Sr)O termination. This result implies that dramatically enhanced oxygen exchange performance could potentially be obtained by suppressing the (La,Sr)O termination and stabilizing highly active CoO termination.
降低固体氧化物燃料电池的工作温度对其商业化至关重要，但受限于阴极氧交换动力学缓慢，这限制了氧还原反应的整体速率。我们使用从头算方法为代表性阴极材料 LaSrCoO 中的氧交换建立了定量的基本反应模型，并预测在操作条件下，从 O 气体在稳定的（001）-SrO 表面上掺入氧的速率限制步骤是 O adatoms 和氧表面空位的横向（表面）扩散。我们预测，在亚稳 CoO 端具有高空位浓度能够实现空位辅助的 O 离解，其速率比富 Sr 的（La，Sr）O 端的速率限制步骤快 10-10 倍。这一结果表明，通过抑制（La，Sr）O 端并稳定高活性 CoO 端，有可能获得显著增强的氧交换性能。
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