Peter Michael Spurgeon

Bio: Peter Michael Spurgeon is an academic researcher. The author has contributed to research in topics: Sulfur. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Investigations of sulfur-silver interactions and mass transport on silver and gold surfaces

Abstract: .................................................................................................................................. vi CHAPTER 1. GENERAL INTRODUCTION ............................................................................... 1 1. Motivation ............................................................................................................................... 1 1.1 Coinage metals ................................................................................................................ 2 1.2 Metal-sulfur complexes ..................................................................................................... 2 2. Experimental details and methods........................................................................................... 3 2.1 Equipment .......................................................................................................................... 3 2.2 Sample materials................................................................................................................ 6 2.3 Data analysis ...................................................................................................................... 9 3. Dissertation organization....................................................................................................... 10 4. References ............................................................................................................................. 11 CHAPTER 2. CHARACTERISTICS OF SULFUR ATOMS ADSORBED ON Ag(100), Ag(110), AND Ag(111) AS PROBED WITH SCANNING TUNNELING MICROSCOPY: EXPERIMENT AND THEORY .................................................................................................. 17 1. Abstract ................................................................................................................................. 17 2. Introduction ........................................................................................................................... 18 3. Methods ................................................................................................................................. 20 3.1 Experimental details ........................................................................................................ 20 3.2 Computational methodology ........................................................................................... 21 4. Experimental results .............................................................................................................. 27 4.1 S/Ag(100): STM results ................................................................................................... 27 4.2 S/Ag(110): STM results ................................................................................................... 30 5. DFT results ............................................................................................................................ 31 5.1. S/Ag(100): DFT results .................................................................................................. 32 5.2. S/Ag(110): DFT results .................................................................................................. 37 5.3. S/Ag(111): DFT results .................................................................................................. 38 6. Discussion ............................................................................................................................. 39 7. Conclusions ........................................................................................................................... 43 8. References ............................................................................................................................. 44 9. Acknowledgements ............................................................................................................... 48 10. Appendix 1: Coverage dependence of S/Ag(100)............................................................... 49 11. Appendix 2: STM tunneling conditions .............................................................................. 57

Shape- and size-specific chemistry of Ag nanostructures in catalytic ethylene epoxidation

Abstract: Catalytic selectivity in the epoxidation of ethylene to form ethylene oxide on alumina-supported silver catalysts is dependent on the geometric structure of catalytically active Ag particles and reaction conditions. Shape and size controlled synthesis of Ag nanoparticles is used to show that silver nanocubes exhibit higher selectivity than nanowires and nanospheres. For a given shape, larger particles offer improved selectivity. The enhanced selectivity toward ethylene oxide is attributed to the nature of the exposed Ag surface facets; Ag nanocubes and nanowires are dominated by (100) surface facet and Ag nanospheres are dominated by (111). Furthermore, the concentration of undercoordinated surface sites is related to diminished selectivity to ethylene oxide. We demonstrate that a simple model can account for the impact of chemical and physical factors on the reaction selectivity. These observations have also been used to design a selective catalyst for the ethylene epoxidation reaction.

Sulfur-induced structural motifs on copper and gold surfaces

Abstract: The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. We choose very specific conditions: very low temperature (5 K), and very low sulfur coverage (≤ 0.1 monolayer). In this region of temperature-coverage space, which has not been examined previously for these adsorbate-metal systems, the effects of individual interactions between metals and sulfur are most apparent and can be assessed extensively with the aid of theory and modeling. Furthermore, at this temperature diffusion is minimal and relatively-mobile species can be isolated, and at low coverage the structures observed are not consumed by an extended reconstruction. The primary experimental technique is scanning tunneling microscopy (STM). The experimental observations presented here—made under identical conditions— together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.