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X-ray spectroscopic and density functional theory studies of small molecules on zinc oxide and copper oxide surfaces :Surface reactivity important to the methanol synthesis reaction

Record Type:	Electronic resources : Monograph/item
Title/Author:	X-ray spectroscopic and density functional theory studies of small molecules on zinc oxide and copper oxide surfaces :
Reminder of title:	Surface reactivity important to the methanol synthesis reaction
Author:	Jones, Paul Max.
Description:	273 p.
Notes:	Adviser: Edward I. Solomon.
Notes:	Source: Dissertation Abstracts International, Volume: 65-04, Section: B, page: 1883.
Contained By:	Dissertation Abstracts International65-04B.
Subject:	Chemistry, Physical.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3128656
ISBN:	0496759183

X-ray spectroscopic and density functional theory studies of small molecules on zinc oxide and copper oxide surfaces :Surface reactivity important to the methanol synthesis reaction
Jones, Paul Max.

X-ray spectroscopic and density functional theory studies of small molecules on zinc oxide and copper oxide surfaces :Surface reactivity important to the methanol synthesis reaction [electronic resource] - 273 p.

Adviser: Edward I. Solomon.

Thesis (Ph.D.)--Stanford University, 2003.

The methanol synthesis reaction (MSR) was probed by exposing ZnO and Cu2O single crystal surfaces to CO, CH2O and CH 3OH and utilizing density functional theory (DFT) to ascertain the electronic structure contributions to bonding. CO is carbon end bound in an eta 1 configuration on these surfaces. DFT calculations of these surface complexes reveal no pi-backbonding in the case of ZnO and very little when bound to the Cu2O surface. Formaldehyde is molecularly chemisorbed (at low temperature) on ZnO, having an oxygen bound eta1 confirmation and no change in the C-O bond length. This surface bond is due to charge donation from the formaldehyde to the 4s and 4p levels of the Zn(II) site. A formyl intermediate was observed on the ZnO(0001) surface upon heating the surface bound formaldehyde. DFT calculations reveal that this intermediate is activated for nucleophilic attack at the oxygen atom, yielding the trans isomer of formaldehyde. Methanol was deprotonated on both ZnO and Cu 2O surfaces. Further reaction of the methoxide to form formate was observed with increasing temperature on the ZnO(0001) crystal surface, but not on the Cu2O surface. DFT calculations attribute the methoxide surface bond to charge donation to the metal ion site, a small C-O bond contraction was observed and no pi-backbonding is calculated. An increase in the net negative charge on the methyl hydrogen atoms is calculated, thus activating them for further reaction. DFT transition state calculations of the MSR reaction coordinate identify a pseudo eta2 bound isomer of formaldehyde as the transition state in the overall barrier in the MSR reaction and is due to the forbidden crossing of levels. The molecular orbitals involved at the crossing are identified and the decrease in the reaction barrier on the surface was assigned to the stabilization of these levels at the crossing by the surface. From these studies the reaction coordinate for methanol synthesis on ZnO, starting with CO, is assembled from the computed DFT total energies.

ISBN: 0496759183Subjects--Topical Terms:

226924
Chemistry, Physical.

X-ray spectroscopic and density functional theory studies of small molecules on zinc oxide and copper oxide surfaces :Surface reactivity important to the methanol synthesis reaction
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