Structure Sensitivity in Enantioselective Surface Chemistry: Tartaric Acid on Copper(110) and Copper(651)(Power of R&S)

Enantioselective heterogeneous catalysis focuses on the synthesis of chiral compounds where one enantiomer is favored over the other. These catalytic reactions are widely studied on high-Miller-index metal surfaces. Surface structure and local chirality have a large effect and influence on the kinetics of enantioselective reactions. This study focuses on understanding the effect of structure sensitivity on the enantioselective decomposition of tartaric acid on chiral copper surfaces. The real structure of copper and platinum high-Miller-index surfaces was investigated using photoemission of adsorbed xenon (PAX). High-Miller-index surfaces can contain surfaces with terrace, step and kink sites which are all catalytically active. PAX was used as an attempt to quantify and characterize these surfaces. A detailed look at the ideal structure of high-Miller-index surfaces is also presented. Surface site definitions are expanded from the typical terrace/step/kink definitions to include nine distinct types of surface sites by using the surface coordination number. Generalized equations for the quantity of each site are described and utilized for generating contour plots of each site across the stereographic triangle.;A new high-throughput method is described with surface structure spread single crystals (S4C) which are spherically curved surfaces that expose a wide range of surfaces vicinal to a central orientation. A library of copper S4C surfaces was created such that three curved surfaces can span the entire stereographic triangle of possible face-centered cubic surface structures. The S4C surfaces are characterized using contour plots of surface sites, laser profilometry to find the real bulk shape of the crystal, Laue x-ray diffraction to find high symmetry points and azimuthal directions and scanning tunneling microscopy for analyzing atomic-scale surface features. These S4C surfaces were created in order to study the structure sensitivity of the super-enantioselective decomposition of tartaric acid. Temperature-programmed desorption experiments were conducted on Cu(110) and Cu(651)R&S surfaces to determine a reaction mechanism that best explains the decomposition reaction. Initial work was performed with tartaric acid dosed onto curved Cu(110) as a basis for later experiments using 2D spatially-resolved x-ray photoelectron spectroscopy to study the effect of surface structure on the enantioselectivity and reaction rate of the decomposition.