Bridging the pressure gap : taking surface science to more realistic pressures

• Main Author: Quin, David John Gilbert
• Published: University of Southampton 2008
• Subjects: 541.33
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484956

Traditional surface science experiments are conducted under ultra high vacuum conditions, this enables surface cleanliness to be strictly controlled and the use of electron based measurements, to determine surface structure and composition. Unfortunately, lftlV conditions are very different from those in real world catalysis (e.g. car exhaust clean-up) and only limited insight can be obtained from such studies. For example, it has been found that certain catalytic species do not exist under UHV conditions. It is an essential step in the progression of surface science to move to more realistic conditions whilst still retaining the simplicity enabled by a UHV cleaned, ideal surface such as a single crystal. this thesis the development of two new pieces of equipment, which bridge this gap, at the SRS at Daresbury Laboratory are presented. The High Pressure Reaction Cell (HPRC), based on the far-IR beamline 13.3 at Daresbury laboratory, enables samples to be cleaned under lJHV conditions before being exposed to pressures, inside the cell, of up to 200 mbar of a chosen gas, without compromising the external vacuum. Far-IR RAIRS, which is useful for adsorbate investigations, is unaffected by the presence of a partial pressure of gas, enabling in-situ measurements as well as postexperiment UHV measurements. Results are presented for investigations into the high pressure oxidation and reduction copper, these are supported by DFT calculations ofthe phonon modes for common copper oxides. The High Ambient Pressure Photoelectron spectroscopY (H.APPY) system is a peripatetic end station designed to allow sample cleaning in UHV, before performing in-situ photoelectron spectroscopy at pressures up to 10-2 mbar. The commissioning experiments in which a commercial supported catalyst was studied are presented. The future of these two newly developed pieces of equipment is discussed alongside the future offar-IR RAIRS as a whole.