| AVS 62nd International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS-WeM |
| Session: | Environmental Interfaces, Ambient Surfaces, In-Operando Studies and Adsorption on 2D Materials |
| Presenter: | Fabrizio Orlando, Paul Scherrer Institut, Switzerland |
| Authors: | F. Orlando, Paul Scherrer Institut, Switzerland A. Waldner, Paul Scherrer Institut and ETH Zürich, Switzerland M.-T. Lee, Paul Scherrer Institut and University of Bern, Switzerland M. Birrer, Paul Scherrer Institut, Switzerland T. Bartels-Rausch, Paul Scherrer Institut, Switzerland C. Proff, Paul Scherrer Institut and ETH Zürich, Switzerland T. Huthwelker, Paul Scherrer Institut, Switzerland A. Kleibert, Paul Scherrer Institut, Switzerland J. van Bokhoven, Paul Scherrer Institut and ETH Zürich, Switzerland M. Ammann, Paul Scherrer Institut, Switzerland |
| Correspondent: | Click to Email |
Near ambient pressure X-ray photoelectron spectroscopy (NAPP) is a powerful tool to investigate elemental composition and chemical specificity of surfaces under reaction conditions that offers tremendous opportunities in environmental science and heterogeneous catalysis research. In the first part of this contribution I will provide a brief outlook on a new analysis chamber for the NAPP endstation at the Swiss Light Source that is designed for in situ XPS and NEXAFS at solid/vapor interfaces under environmentally relevant conditions of temperature and pressure (up to 20 mbar and 100% relative humidity) [1]. The flow-tube design of this new chamber allows to perform in situ measurements at high pressure and UHV conditions one after the other in the same analysis cell, while at the same time reducing the exposed volume and surface area of the analysis cell. Moreover, this chamber features (i) a direct access from a gas dosing system down to the sample, allowing for the admission of sticky gases with reduced wall effects, and (ii) a UV laser setup, providing the opportunity to investigate photoactive materials under atmospherically relevant conditions of pressure and light with reduced extent of gas phase photochemistry induced by the UV-light. We have used this novel chamber to investigate photocatalysis on TiO2, which is a component of natural mineral dust that represents an important reactive aerosol in the atmosphere affecting the ozone budget and the climate. In this context, adsorption of water and hydroxylation of the surface, which are key aspects to understand TiO2 photocatalysis in the environment, offer still major open questions. Earlier NAPP studies have provided important insight into the nucleation of water on this surface [2]. In a recent study we have quantified the effect of humidity on ozone-induced band bending on the TiO2(110) surface [3], and found interesting changes in XPS and NEXAFS spectra indicative of changes in the hydrogen bonding structure in multilayers of water [4]. I will discuss our most recent NAPP investigation on the influence of UV light and humidity on the adsorption of water on a TiO2 powder sample surface. Our results indicate an enhancement of water adsorption under UV irradiation, which might be the basis to explain light-induced superhydrophilicity previously observed on TiO2-based nanomaterials. I will also briefly illustrate an application study on the uptake of trace gases on ice surface.
References
[1] F. Orlando et al., submitted.
[2] G. Ketteler et al., J. Phys. Chem C 111, 8278 (2007).
[3] M. Lampimäki et al., ChemPhysChem 14, 241 (2013)
[4] M. Lampimäki et al., J. Phys. Chem. C 119, 7076 (2015).