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Observing the Electrochemical Oxidation of Co Metal at the Solid/Liquid Interface Using Ambient Pressure X-ray Photoelectron Spectroscopy
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2017-09-08 00:00:00 , DOI: 10.1021/acs.jpcb.7b05982
Yong Han 1, 2 , Stephanus Axnanda 3 , Ethan J. Crumlin 3 , Rui Chang 1 , Baohua Mao 1 , Zahid Hussain 3 , Philip N. Ross 4 , Yimin Li 1, 2 , Zhi Liu 1, 2
Affiliation  

Recent advances of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) have enabled the chemical composition and the electrical potential profile at a liquid/electrode interface under electrochemical reaction conditions to be directly probed. In this work, we apply this operando technique to study the surface chemical composition evolution on a Co metal electrode in 0.1 M KOH aqueous solution under various electrical biases. It is found that an ∼12.2 nm-thick layer of Co(OH)2 forms at a potential of about −0.4 VAg/AgCl, and upon increasing the anodic potential to about +0.4 VAg/AgCl, this layer is partially oxidized into cobalt oxyhydroxide (CoOOH). A CoOOH/Co(OH)2 mixture layer is formed on the top of the electrode surface. Finally, the oxidized surface layer can be reduced to Co0 at a cathodic potential of −1.35 VAg/Cl. These observations indicate that the ultrathin layer containing cobalt oxyhydroxide is the active phase for oxygen evolution reaction (OER) on a Co electrode in an alkaline electrolyte, consistent with previous studies.

中文翻译:

使用环境压力X射线光电子能谱观察Co / Co在固/液界面处的电化学氧化

环境压力X射线光电子能谱(AP-XPS)的最新进展使得能够直接探测电化学反应条件下在液/电极界面处的化学组成和电势分布。在这项工作中,我们应用这种操作技术研究了在各种电偏压下0.1 M KOH水溶液中Co金属电极上表面化学成分的演变。发现在大约-0.4 V Ag / AgCl的电势下形成了厚约1.2.2 nm的Co(OH)2层,当阳极电势增加到大约+0.4 V Ag / AgCl时,该层被部分氧化变成羟基氧化钴(CoOOH)。CoOOH / Co(OH)2混合物层形成在电极表面的顶部。最后,可以在-1.35 V Ag / Cl的阴极电位下将氧化的表面层还原为Co 0。这些观察结果表明,与先前的研究一致,含有羟基氧化钴的超薄层是碱性电解质在Co电极上进行氧放出反应(OER)的活性相。
更新日期:2017-09-08
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