Marjorie A. Langell
Date of this Version
Christensen, G. L., Synthesis, Characterization, and Catalytic Activity of copper Palladium Oxide Solid Solutions, master's thesis, University of Nebraska-Lincoln, (2018)
CuxPd1-xO forms a homogeneous solid solution over the wide range of 0 ≤ x ≤ 0.725 in which compositional variation can be correlated with structural and chemical environmental changes. After a small lag at low Cu2+ concentrations, where the lattice cell parameters are pinned to that of the pure PdO structure, CuxPd1-xO lattice parameters follow Vegard’s law in which the cell volume decreases linearly with x, indicating a homogenous solution in which Cu2+ randomly replaces the larger Pd2+ cation. The crystal structure also undergoes an increase in the c/a cell ratio, which relaxes the tetragonal distortion around the metal cation and shifts the metal-oxygen distance towards that of pure CuO (tenorite). X-ray photoelectron spectroscopy (XPS) shows a linear increase in Pd2+ 3d and Cu2+ 2p binding energies with increased Cu2+, a result of the increased Madelung energy and relaxation effects which occur during the photoemission process. XPS and Auger Electron Spectroscopy (AES) indicate that the surface composition is comparable to that of the bulk, and copper XPS Auger parameter analysis confirms a different, and variable, environment for copper in CuxPd1-xO than is found in pure tenorite.
Solid solutions of CuxPd1-xO have been prepared with x values of 0, 0.2, 0.4, 0.6, and 1 for use as catalysts in the dehydrogenation of isopropanol to form acetone. Solid solution catalysts were shown to be less efficient catalysts when compared to mixtures of equal atomic composition. SEM images were obtained and showed morphology changes after heating of the samples. Surface area of the catalysts was determined by BET. UV/VIS was used to determine reactant and product concentrations. XPS data were obtained on the catalysts before and after the reactions, showing reduction of the catalyst occurred during catalysis.
Advisor: Marjorie A. Langell