ELECTRONIC EFFECTS OF CHEMISORPTION ON A POWDERED ZINC OXIDE CATALYST.
Technical rept. Sep 68-Sep 70,
PRINCETON UNIV N J
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The report presents a general discussion of electronic surface states and their possible electronic and catalytic effects. It also presents a method by which the temperature-dependence of the catalysts conductivity can be used to elicit information on the disposition of the surface states relative to the bulk band structure. The catalyst was ZnO in powder form and an impedance technique was used to measure its conductivity under single gas CO and O2 and differential reaction 2CO 02 yields 2CO2 ambients. Oxygen acceptor surface states appear to have a dominant influence over the catalysts conductivity even at O2 pressures as low as 0.00001 torr and in reaction mixture containing greater than 4 parts CO to one part O2. The apparent donor effect of adsorbed CO appears to result from the interaction with adsorbed or lattice oxygen rather than from the formation of a donor-like CO adsorption state. The experimental measurements tend to confirm the energy band structure model of this semiconductor catalyst and reveal certain features of interest for the electronic theory of catalysis. However, it does appear that powder systems may be too complex to deal with quantitatively at the present stage of development of electronic surface state theories. Author
- Atomic and Molecular Physics and Spectroscopy