Characterization of Electrode Activity through Photoelectron Spectroscopy: A Coordinated Synchrotron and Laboratory XPS Approach to Electrocatalysis

该项目由分析和表面化学项目资助，研究了小分子氧化/还原反应中二、三元电极催化剂的核心能级电子结合能转移与电催化反应活性之间的关系。催化剂是由过渡金属自发沉积在铂、钌、钯和金单晶衬底上形成的。有强有力的证据表明，金属在二维和三维纳米岛中排列，正如原位STM监测的那样。这项工作是在伊利诺伊大学的Andrzej Wieckowski实验室和威斯康星大学麦迪逊分校的同步辐射中心（SRC）进行的；在低和极低金属覆盖水平测量结合能位移需要强同步x射线光。此外，同步辐射的高分辨率使得精确测量结合能位移成为可能。实验（Wieckowski UIUC， PI）和理论（Bagus UNT, co-PI）之间紧密而直接的联系是本项目的关键要素，它基本上决定了测量的核心能级结合能的化学和物理意义。同步加速器的工作带来了高x射线强度、高分辨率和低探测水平。总的来说：电化学表征决定了反应性，同步加速器XPS和实验室XPS产生了结合能位移，理论提供了在所研究表面的反应性和电子结构之间的定量联系。这些电子水平的结果使人们对过渡金属和贵金属双金属催化剂如何在电催化反应中起作用有了清晰的基础科学和应用意义。所研究的材料有望成为小分子燃料电池中有效的氧化和还原催化剂。因此，从这些基础研究中获得的信息可能有助于改进燃料电池催化系统的设计。

This project, funded by the Analytical and Surface Chemistry Program, addresses the correlation between core level electron binding energy shifts and electrocatalytic reactivity at binary and ternary electrode catalysts for small molecule oxidation/reduction reactions. The catalysts are formed by spontaneous deposition of transition metals on single crystal substrates of Pt, Ru, Pd and Au. There is strong evidence that the admetals are arranged in two- and three-dimensional nanoislands, as monitored by in situ STM. This work is carried out in the laboratory of Andrzej Wieckowski at the University of Illinois and at the Synchrotron Radiation Center (SRC) at the University of Wisconsin-Madison; the intense synchrotron x-ray light is needed to measure the binding energy shifts at the low and very low admetal coverage levels. Moreover, the high resolution of the synchrotron radiation makes possible accurate measurements of the binding energy shifts. A strong and direct link between experiment (Wieckowski UIUC, PI) and theory (Bagus UNT, co-PI) is a key element of this project that basically determines the chemical and physical significance of the measured core level binding energies. The synchrotron work brings high x-ray intensity, high resolution, and low detection level for the admetal coverage. Overall: electrochemical characterization determines reactivity, synchrotron XPS and laboratory XPS yield the binding energy shifts, and theory provides quantitative link between the reactivity and electronic structure of the studied surfaces. These electronic-level results produce understanding of how transition and noble metal bimetallic catalysts work for electrocatalytic reactions of clear basic-science and applied significance. The materials studied show promise as effective oxidation and reduction catalysts in small molecule fuel cell applications. Therefore, information obtained from these fundamental investigations may aid in the design of improved fuel cell catalytic systems.