The development and utilization of inelastic electron tunneling spectroscopy as a surface vibrational probe with an emphasis on the study of chemisorption and heterogeneous catalysis

• Main Author: Bowser, William Matthew
• Format: Others
• Language: en
• Published: 1980
• Online Access: https://thesis.library.caltech.edu/4985/1/Bowser_wm_1980.pdf; Bowser, William Matthew (1980) The development and utilization of inelastic electron tunneling spectroscopy as a surface vibrational probe with an emphasis on the study of chemisorption and heterogeneous catalysis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/w6b6-t291. https://resolver.caltech.edu/CaltechETD:etd-12132006-131809 <https://resolver.caltech.edu/CaltechETD:etd-12132006-131809>

Inelastic electron tunneling spectroscopy (IETS) has been used to investigate the vibrational structure of molecular species bound to, or contained in, the insulating layer of Al-insulator Pb tunnel junctions. The insulating layer, prepared by the exposure of the Al electrode to an oxygen plasma discharge, was studied via IETS and was found to be an oxide rather than a hydroxide. An oxide with appreciable hydroxide content could be prepared under certain conditions. An X-ray photoelectron spectroscopic (XPS) study of this oxide layer was also carried out to further facilitate comparison to commercial aluminas. IETS was used to investigate the chemisorption on this oxide of phenol and three derivatives of phenol: catehol, resorcinol and hydroquinone. Phenol adsorbs as a phenixide ion, catechol and resorcinol lose both of their acidic protons upom chemisorption, whereas hydroquinone only loses one proton, bonding as a mono-ion. This study demonstrated the high sensitivity and resolution of IETS. IETS was also used in the study of supported metal catalysts. The adsorption of ethanol on silver particles supported on alumina was studied, extending the use of IETS in supported metal catalysis. An important area of current research is concerned with the fixing of metal cluster compounds on substrated to form catalysis. IETS was used to study the interaction of [RhCl(CO)2]2 on alumina, the first reported study of a metal carbonyl complex via IETS. This complex decomposes upon chemisorption, leaving, predominantly, isolated Rh(CO)2 species on the surface. In contrast, Ru3(CO)12 is seen via IETS, to retain its molecular structure upon adsorption on alumina. A method for heating the IETS sample easily and quickly is also presented.