McPherson Ian J, Ash Philip A, Jones Lewys, Varambhia Aakash, Jacobs Robert M J, Vincent Kylie A
Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
Department of Materials, University of Oxford, 16 Parks Road, Oxford OX1 3PH, U.K.
J Phys Chem C Nanomater Interfaces. 2017 Aug 17;121(32):17176-17187. doi: 10.1021/acs.jpcc.7b02166. Epub 2017 Jul 24.
The oxidation of adsorbed CO is a key reaction in electrocatalysis. It has been studied extensively on both extended model surfaces and on nanoparticles; however, correlation between the two is far from simple. Molecular insight into the reaction is often provided using in situ IR spectroscopy; however, practical challenges mean in situ studies on nanoparticles have yet to provide the same level of detail as those on model surfaces. Here we use a new approach to in situ IR spectroscopy to study the mechanism of CO adlayer oxidation on a commercial carbon-supported Pt catalyst. We observe bipolar IR absorption bands but develop a simple model to enable fitting. Quantitative analysis of band behavior during the oxidation prepeak using the model agrees well with previous analysis based on conventional absorption bands. A second linear CO band is observed during the main oxidation region and is assigned to the distinct contribution of CO on step as opposed to terrace sites. Analysis of the step and terrace CO bands during oxidation shows that oxidation begins on the terraces of the nanoparticles before CO on steps is removed. Further correlation of this behavior with the current shows that step CO is only lost in the first of the two main oxidation peaks.
吸附态CO的氧化是电催化中的一个关键反应。在扩展模型表面和纳米颗粒上都对其进行了广泛研究；然而，两者之间的关联远非简单。通常使用原位红外光谱来深入了解该反应；然而，实际挑战意味着对纳米颗粒的原位研究尚未提供与模型表面研究相同程度的细节。在此，我们采用一种新的原位红外光谱方法来研究商用碳载Pt催化剂上CO吸附层的氧化机理。我们观察到双极性红外吸收带，但开发了一个简单模型以实现拟合。使用该模型对氧化预峰期间谱带行为进行的定量分析与基于传统吸收带的先前分析结果吻合良好。在主要氧化区域观察到第二条线性CO谱带，它被归因于CO在台阶位点而非平台位点的独特贡献。对氧化过程中台阶和平台CO谱带的分析表明，纳米颗粒的平台上的氧化在台阶上的CO被去除之前就已开始。这种行为与电流的进一步关联表明，台阶CO仅在两个主要氧化峰中的第一个峰中消失。
