Water on Metal Oxide Surfaces
Zirconia (ZrO2) is a wide band-gap (5.0-5.5 eV) transition metal oxide with novel and useful physical properties. ZrO2 is used in a number of applications, which include semiconductor substrates, damage resistant optical coatings, high temperature solid oxide fuel cells and oxygen sensors used in automobile exhaust systems. Zirconium oxide is also present on the surface of nuclear fuel rods. There have been a number of investigations which study the radiation induced interfacial reactions that occur on the surface of zirconia. Due to its unique electronic properties zirconia is a good candidate for hydrogen production.
Current Research
An ultrahigh vacuum (UHV) system is being set up to monitor the catalytic decomposition of water to hydrogen from zirconia nanoparticles in the monoclinic and tetragonal phase. This system will also monitor the hydrogen production from titanium dioxide (TiO2) in order to compare the different yields. Later, alkali metals will be added to the zirconia to compare the yields with the earlier investigations. The exciting light source will be a 254 nm mercury lamp. A quadropole mass spectrometer will be used to measure the hydrogen yield.
Future Work
Electron stimulated desorption (ESD) measurements will be made on water covered ZrO2. In ESD an incident electron beam excites a bonding electron into an antibonding or nonbonding state. As a result the potential between the adsorbate and substrate becomes repulsive and atoms begin to desorb from the surface. The ions that are desorbed can be detected by a time of flight mass spectrometer. Knowing the kinetic energies as well as the amount of water coverage, the mechanism responsible for desorption can be determined. This can also provide information about the zirconia surface and how water adsorbs to it. The neutrals will be detected by the two laser technique; resonance enhanced multiphoton ionization (REMPI) spectroscopy. This detection method will be used to determine the relative populations in various internal states.
Members on Project
Marcus C. Johnson, Michael Poston and Alex Aleksandrov
Collaborators
Z. John Zhang, School of Chemistry and Biochemistry, Georgia Institute of Technology
Funding
The Department of Energy