Rational catalyst design for the ammonia decomposition reaction

THESIS
Rational catalyst design for the ammonia decomposition reaction
by Hansgen, Danielle Ann, Ph.D., UNIVERSITY OF DELAWARE, 2011, 188 pages; 3473687
Abstract:
The ammonia decomposition reaction was explored through multiscale microkinetic modeling for a number of transition metal catalysts, including Pt, Pd, Ir, Ni, Rh, Co, Ru, Re, and Mo, to better understand the reaction mechanism.
An understanding of the reaction mechanism and electronic properties of these metals has given insight into how to tailor catalysts to improve catalytic activity for this reaction. The mechanism consists of 12 elementary reaction steps and 5 surface species, namely N, H, NH, NH2, and NH3. For many of the metals, a large portion of the surface is covered by adsorbates. For these metals, repulsive adsorbate-adsorbate interactions were found to change the binding energies of the surface species, thereby changing the elementary reaction activation barriers and modifying the catalytic activity. Coverage dependent atomic heats of chemisorption were calculated through density functional theory (DFT) using the Vienna ab-initio Simulation Package (VASP) for the various transition metal catalysts. Coverage dependent molecular binding energies and activation barriers were calculated through the bond-order conservation (BOC) method.
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