<p>A fundamental understanding of
heterogeneous catalysis requires analysis of model catalytic surfaces in tandem
with complex technical catalysts. This work was divided in three areas, 1-
preparation and characterization of model surfaces synthesized by vapor
deposition techniques, 2- kinetic evaluation of model catalysts for formic acid
decomposition and dry methane reforming, 3- characterization and kinetic
evaluation of technical catalysts for the water gas shift reaction.</p>
<p>In the first project, model PdZn
intermetallic surfaces, a relevant catalyst for propane dehydrogenation, were
prepared using an ALD approach. In this work, model surfaces were synthesized
by exposing Pd(111) and Pd(100) surfaces to diethylzinc at ca. 10<sup>-6 </sup>mbar.
Several different surface structures were identified by careful control of the
deposition temperature of the substrate. Modifications in the adsorption
properties of these surfaces towards carbon monoxide and propylene coincided
with the structure of the PdZn surface layer. </p>
<p>In the second project, formic acid
decomposition kinetics were evaluated on model Pt catalysts. Formic acid
decomposition was found to be structure-insensitive on Pt(111), Pt(100), and a
polycrystalline foil under standard reaction conditions. CO selectivity
remained < 1% for conversions <10%. Additionally, inverse Pd-Zr model
catalysts were prepared by ALD of zirconium-t-butoxide (ZTB). Depending on
treatment conditions, either ZrO<sub>x</sub>H<sub>y</sub> or ZrO<sub>2</sub>
overlayers or Zr as sub-nanometer clusters could be obtained. The activity of
the model catalyst surface towards dry reforming of methane if the initial
state of the zirconium is metallic. </p>
<p>In the third project, Au/Fe<sub>3</sub>O<sub>4</sub>
heterodimer catalysts were characterized for their thermal stability. In-situ
TEM and XPS characterization demonstrates that the gold nanoparticles transform
into gold thin films that wet the Fe<sub>3</sub>O<sub>4</sub> surface as the
reduction of the oxide proceeds. DFT calculations show that the adhesion energy
between the Au film is increased on a partially reduced Fe<sub>3</sub>O<sub>4</sub>
surface. Additionally, Pt/Nb<sub>2</sub>CT<sub>x</sub> catalysts were
characterized and kinetics evaluated for the water gas shift reaction. XPS and
TEM characterization indicates that a Pt-Nb surface alloy is formed under
moderate reduction temperatures, 350<sup>O</sup>C. Water-gas shift reaction
kinetics reveal that the alloy-MXene interface exhibit high H<sub>2</sub>O
activation ability compared to a non-reducible support or bulk niobium carbide.
</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7792178 |
| Date | 10 June 2019 |
| Creators | Cory A. Milligan (5930045) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/FUNDAMENTAL_INSIGHTS_OF_PLANAR_AND_SUPPORTED_CATALYSTS/7792178 |
Page generated in 0.0024 seconds