| AVS 62nd International Symposium & Exhibition | |
| In-Situ Spectroscopy and Microscopy Focus Topic | Tuesday Sessions |
| Session IS+AS+SA+SS-TuM |
| Session: | In-situ Studies of Solid-liquid Interfaces |
| Presenter: | Beomgyun Jeong, Lawrence Berkeley National Laboratory (LBNL) |
| Authors: | B. Jeong, Lawrence Berkeley National Laboratory (LBNL) M. Favaro, Lawrence Berkeley National Laboratory (LBNL) P.N. Ross, Lawrence Berkeley National Laboratory (LBNL) Z. Hussain, Lawrence Berkeley National Laboratory (LBNL) Z. Liu, Shanghai Institute of Microsystem and Information Technology, China B.S. Mun, Gwangju Institute of Science and Technology, Republic of Korea J. Lee, Gwangju Institute of Science and Technology, Republic of Korea E.J. Crumlin, Lawrence Berkeley National Laboratory (LBNL) |
| Correspondent: | Click to Email |
A catalyst is defined as a substance that enhances a reaction rate without changing its chemical state. However, often the chemical state of a catalyst surface undergoes changes during the reaction, leading to the degradation of catalyst performance. These phenomena are particularly significant in electrocatalysis in which reaction occurs at solid/liquid interface with electrical potential as an activation energy to drive the reaction. In order to understand the mechanism of catalyst degradation, it is important to have a capability to observe the chemical states of electrode and various chemical species in electrolyte during the reaction taking place at the solid/liquid interface. In order to explore this region, we have developed a new experimental approach [1], using ambient pressure XPS (AP-XPS) coupled with “tender” X-rays (in the range between 2.5 and 7.0 keV) at the Advanced Light Source BL 9.3.1, Lawrence Berkeley National Laboratory. Because of the relatively high kinetic energy of the incoming photons, ‘tender’ X-rays allow probing solid/liquid interfaces through thin electrolyte films characterized by a thickness of 10-30 nm. This unique functionality allows the ability to simultaneously correlate the electrocatalytic activity of electrodes to both the chemical modifications of the electrode surface, and the electrolyte.
This talk will provide details on in-situ and operando AP-XPS measurements on the chemical modifications of polycrystalline Pd surface studied at different electrochemical potentials. Pd is a cost-effective materials alternative to Pt showing similar electrocatalytic property of Pt in various reactions, such as oxygen reduction and electrooxidation of hydrogen and formic acid. On the other hand, it is well known that the Pd activity decreases faster than that of Pt especially in formic acid oxidation [2]. This phenomenology could be understood by the direct observation of the Pd surface chemistry evolution at electrified solid/liquid interface. We will discuss the performance of the Pd electrode in two different aqueous electrolytes, in particular in an alkaline medium and in a formic acid solution, an electroactive liquid organic molecule. We believe that our findings represent a step forward in the rationalization of the electrocatalytic behavior of Pd.
[1] S. Axnanda, E.J. Crumlin et al., Sci. Rep. 5 (2015) 9788.; b. E.J. Crumlin et al., in preparation.
[2] H. Jeon, S. Uhm, B. Jeong, J. Lee, Phys. Chem. Chem. Phys. 13 (2011) 6192.