Towards the direct instrumental identification of active electrocatalytic sites using scanning tunneling microscopy

点击翻译按钮获取中文摘要

A deeper understanding of complex objects of nature is not achievable without the development of new informative but at the same time affordable research tools, methodologies and procedures. Original and powerful approaches for probing and modeling will most likely remain pillars controlling the advances in materials science. In this project, we propose an approach for experimental identification of so-called active sites at the surface of heterogeneous electrocatalysts using electrochemical scanning tunneling microscopy. The project utilizes the basic idea that under reaction conditions the parameters defining the tunneling barrier over the catalytically active site in contact with liquid electrolytes will be different, and, importantly, vary with time (e.g. due to approaching reactants and/or departing products), compared to those over the inactive sites. Therefore, the tunneling current measured between the tip and the sample under potential control should also change with time in a different way revealing local processes. By comparing the tunneling current as a function of time and tip-to-surface distance over different surface sites, it would be possible to elucidate the location of the catalytic centers. Our preliminary results support this basic idea. Low-index and high-index single crystal electrodes with quasi-periodic surface structures and very low surface mobility of atoms, nanostructured systems, as well as catalytic reactions important for future sustainable energy provision will be used in this project as model objects and reactions, respectively. Quantum chemistry calculations will be used (in collaboration) to clearly reveal the underlying physical foundations of the method, to support the quantitative interpretation of the experimental data regarding the local catalytic activity, and to iteratively improve the methodology.