| AVS 63rd International Symposium & Exhibition | |
| In-Situ and Operando Spectroscopy and Microscopy for Catalysts, Surfaces, & Materials Focus Topic | Thursday Sessions |
| Session IS-ThA |
| Session: | Ambient Pressure Photoelectron Spectroscopy and Scanning Probe Techniques |
| Presenter: | Christoph Cobet, Johannes Kepler University, Austria |
| Authors: | C. Cobet, Johannes Kepler University, Austria M.-H. Chien, Johannes Kepler University, Austria R. Sharif, Johannes Kepler University, Austria V. Solokha, Johannes Kepler University, Austria Gh. Barati, Johannes Kepler University, Austria K. Hingerl, Johannes Kepler University, Austria |
| Correspondent: | Click to Email |
We combine spectroscopic ellipsometry (SE), reflection anisotropy spectroscopy (RAS), and a homemade electrochemical scanning tunneling microscope (EC-STM) to study the surface of electrodes on the atomic level in liquids i.e. electrochemical environments. This combination of in-situ methods provides complementary information in comparison to conventional cyclic voltammetry (CV). While in CV the integrated charge and ion-exchange is measured, EC-STM provides direct snapshots of the surface morphology and electron corrugation. Polarization optical spectroscopy, on the other hand, is known for high surface/interface sensitivity regarding chemical modifications, sub-monolayer film formation and morphology transformations. The optical information can be additional recorded with almost the same time resolution like in conventional CV and allows the study of reaction kinetics. Thus it is finally possible to relate measured Faraday-currents to different surface processes.
Here, we report on the results on Cu single crystal surfaces of different orientation in halide solutions. The observed processes include halide adsorption, Cu(I) and Cu(II) dissolution, hydrogen evolution, as well as the initial formation of CuO. These studies are motivated by questions concerning e.g. the corrosion behavior and the catalytic functionality of Cu surfaces. The adsorption of Cl on Cu(110) at anodic potentials for example minimizes the surface energy by a formation of monoatomic steps parallel to the [001]-direction which finally ends up in a faceting of the surface. It turns out that some of the characteristic redox peaks in CV correlate with the surface transformation while others relate to a Cu(I) dissolution. The observed morphology transformations compares in parts with the oxide/chloride induced surface structures as measured UHV. This behavior is only observed at the more “open” and instable (110) surface. The (111) surface, in contrast, retains a smooth surface upon halide adsorption but with a distinct surface reconstruction. At more cathodic potentials we could monitor the hydrogen absorption and the hydrogen gas evolution at Cu surface by RAS and SE, respectively.