Han Yong, Axnanda Stephanus, Crumlin Ethan J, Chang Rui, Mao Baohua, Hussain Zahid, Ross Philip N, Li Yimin, Liu Zhi
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , Shanghai 200050, People's Republic of China.
School of Physical Science and Technology, Shanghai Tech University , Shanghai 200031, China.
J Phys Chem B. 2018 Jan 18;122(2):666-671. doi: 10.1021/acs.jpcb.7b05982. Epub 2017 Sep 8.
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) forms at a potential of about -0.4 V, and upon increasing the anodic potential to about +0.4 V, this layer is partially oxidized into cobalt oxyhydroxide (CoOOH). A CoOOH/Co(OH) mixture layer is formed on the top of the electrode surface. Finally, the oxidized surface layer can be reduced to Co at a cathodic potential of -1.35 V. 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.
常压X射线光电子能谱（AP-XPS）的最新进展使得在电化学反应条件下直接探测液体/电极界面处的化学成分和电势分布成为可能。在这项工作中，我们应用这种原位技术来研究在各种电偏压下0.1 M KOH水溶液中Co金属电极上的表面化学成分演变。结果发现，在约-0.4 V的电位下形成了一层约12.2 nm厚的Co(OH)层，当将阳极电位提高到约+0.4 V时，该层部分氧化成羟基氧化钴（CoOOH）。在电极表面顶部形成了CoOOH/Co(OH)混合层。最后，在-1.35 V的阴极电位下，氧化表面层可还原为Co。这些观察结果表明，含有羟基氧化钴的超薄层是碱性电解质中Co电极上析氧反应（OER）的活性相，这与先前的研究一致。
