X-ray photoelectron spectroscopy; surface chemistry; Aerosol; Catalysis; synchrotron
Brown Matthew A., Redondo Amaia Beloqui, Jordan Inga, Duyckaerts Nicolas, Lee Ming-Tao, Ammann Markus, Nolting Frithjof, Kleibert Armin, Huthwelker Thomas, Machler Jean-Pierre, Birrer Mario, Honegger Juri, Wetter Reto, Wörner Hans Jakob, van Bokhoven Jeroen A. (2013), A new endstation at the Swiss Light Source for ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy measurements of liquid solutions, in Review of Scientific Instruments
, 84(7), 073904-8-8.
Brown Matthew A., Duyckaerts Nicolas, Beloqui Redondo Amaia, Jordan Inga, Nolting Frithjof, Keibert Armin, Ammann Markus, Woerner Hans Jakob, van Bokhoven Jeroen A., Abbas Zareen (2013), Effect of Surface Charge Density on the Affinity of Oxide Nanoparticles for the Vapor-Water Interface, in LANGMUIR
, 29(16), 5023-5029.
Brown Matthew A., Jordan Inga, Beloqui Redondo Amaia, Kleibert Armin, Woerner Hans Jakob, van Bokhoven Jeroen A. (2013), In situ photoelectron spectroscopy at the liquid/nanoparticle interface, in SURFACE SCIENCE
, 610, 1-6.
X-ray photoelectron spectroscopy (XPS) performed at pressures up to 20 mbar (here referred to as near-ambient pressure photoemission, NAPP) is an emerging tool that allows probing the chemistry of surfaces that are relevant to catalysis and the environment under nearly realistic reactant and pressure conditions, thus largely overcoming the pressure gap that separates the basic UHV-based surface science technique and the conditions of real applications.NAPP at PSI will push the molecular level surface chemistry on particles, ice and other environmental surfaces, which are relevant to understanding atmospheric composition change and to assessing the impact of human activities on climate change. The second target research field is catalysis. Understanding how a catalyst functions, through the development of structure-performance relations, enables improving existing processes and, ultimately, the design of new better ones. These developments are required to produce energy and chemicals in a sustainable manner in the nearest future.The basic concept of NAPP is that the sample is exposed to a gas or liquid environment and that the photo-electrons are sampled through a differentially pumped electrostatic lens system into an electron energy analyzer held at UHV. Scattering of the electrons by the gas phase molecules and the pressure field distor-tion around the sampling aperture into the lower pressure lens system provides constraints on the maximum pressures attainable. The only synchrotron user facilities holding a high pressure XPS end station are highly oversubscribed beamlines at the Advanced Light Source (ALS). Only a handful of further synchrotron-based or lab X-ray source based instruments exist worldwide.We propose to set up a NAPP instrument as a mobile end station prepared for the SIM and PHOENIX beam lines of the Swiss Light Source. We intend to use the instrumentation to solve scientific questions that are relevant to catalysis and energy conversion and the environment. For environmental surface chemistry, the long-term focus is establishing a molecular level description of the climate and air pollution impact of atmospheric particles. This requires in situ photoemission experiments with solid materials at high water vapour pressure, on aqueous solution droplet trains and submicron particle beams to allow kinetic and photochemical experiments. The latter configurations circumvent major obstacles related to beam damage of radiation sensitive environmental materials. In the field of catalysis, the ultimate aim is to measure industrially relevant catalyst structures under catalytic conditions that have realistic flow dynamics. The high photon flux available at the SIM beam line is of paramount importance for measuring nano-particle beams, droplet trains, and catalysts with low content of active component while the broad energy range of the PHOENIX beamline provides unique opportunities for studies that require higher incident energies.The differentially pumped electrostatic lens system, which allows high transmission to a traditional electron kinetic energy analyzer is commercially available. The first innovation of our proposal lies in expanding the photoelectron kinetic energy to 7 keV to better compare surface vs. bulk composition and to get a handle on buried solid/liquid interfaces. The second innovative aspect is the sample environments we are envisioning. While other instruments under development at different synchrotron facilities, such as ALS, ALBA or Brookhaven, concentrate on analyzing samples both under UHV and elevated pressure using the same configuration, we propose to design experimental chambers that accommodate novel sample environments such as liquid jets and catalytic flow reactors. On the long-term, as a most significant innovation, we will develop experiments for NAPP on free nanoparticle beams. The development of a liquid jet or a controlled train of nanoparticles of solid or soft matter will allow timed experiments. This opens the path to fast kinet-ics experiments, such as pump-probe and other configurations.