Browsing by Author "Byron, Carly"
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Item Adsorption and Thermal Decomposition of Triphenyl Bismuth on Silicon (001)(Journal of Physical Chemistry C, 2023-08-24) Lundgren, Eric A. S.; Byron, Carly; Constantinou, Procopios; Stock, Taylor J. Z.; Curson, Neil J.; Thomsen, Lars; Warschkow, Oliver; Teplyakov, Andrew V.; Schofield, Steven R.We investigate the adsorption and thermal decomposition of triphenyl bismuth (TPB) on the silicon (001) surface using atomic-resolution scanning tunneling microscopy, synchrotron-based X-ray photoelectron spectroscopy, and density functional theory calculations. Our results show that the adsorption of TPB at room temperature creates both bismuth–silicon and phenyl–silicon bonds. Annealing above room temperature leads to increased chemical interactions between the phenyl groups and the silicon surface, followed by phenyl detachment and bismuth subsurface migration. The thermal decomposition of the carbon fragments leads to the formation of silicon carbide at the surface. This chemical understanding of the process allows for controlled bismuth introduction into the near surface of silicon and opens pathways for ultra-shallow doping approaches.Item Attachment Chemistry of 4-Fluorophenylboronic Acid on TiO2 and Al2O3 Nanoparticles(Chemistry of Materials, 2022-12-13) Byron, Carly; Silva-Quinones, Dhamelyz; Sarkar, Sucharita; Brown, Scott C.; Bai, Shi; Quinn, Caitlin M.; Grzenda, Zachary; Chinn, Mitchell S.; Teplyakov, Andrew V.Surface modification of nanoparticulate TiO2 and Al2O3 materials with 4-fluorophenylboronic acid is investigated in order to both evaluate the novel surface modification schemes and develop spectroscopic labels for surface characterization. The chemistry of the modification is followed on all these surfaces using X-ray photoelectron spectroscopy, multinuclear (11B, 19F, and 13C) solid-state and solution NMR, and infrared spectroscopy to determine the binding modes of this compound using boron and fluorine as probe atoms. Density functional theory model calculations are utilized to visualize predicted surface species and to interpret the results of spectroscopic measurements. A comparison is made among TiO2 rutile, TiO2 anatase, and γ-Al2O3. On all three materials, the modification proceeds via the boronic functional groups, with metal oxide-controlled surface chemistry. The bonding configuration depends on the material and is dominated by a monodentate species for titania and by bidentate species for alumina. The surface structures determined to form on all the oxide semiconductors investigated suggest that sensitization or monolayer doping approaches with a well-defined chemical interaction via a boronic functionality can be developed.Item Exploring the chemistry of metal/metal oxide catalysts: an insight into nanoscale surface interactions(University of Delaware, 2023) Byron, CarlyThe work outlined in this dissertation is dedicated to the surface chemistry of promoted metal nanoparticle catalysts for dry reforming of methane (DRM). The main part of this work focuses on the effect of promoters on platinum and nickel active catalysts and understanding how the change in surface chemistry affects the mechanism of the DRM reaction. We have identified several promoters that improve the DRM activity by tuning the surface chemistry; boron promoter with platinum catalyst and transition metal promoters with nickel catalyst. The addition of promoter sites led to the migration of coke deposits away from active sites, improved surface activation of CO2, and morphological control over the coke deposits. This work is necessary because growing concern over the effects of climate change has necessitated research into potential fossil fuel replacements. The current energy infrastructure already supports hydrocarbon fuel sources. However, researchers' current challenge is the ability to produce fuel in a carbon-neutral process using inexpensive catalytic materials. Heterogeneous catalysis is paramount to solving the energy problem, and the chemistry of catalytic surfaces must be optimized to achieve carbon-based fuel production that can replace fossil fuels long term. Noble metals and transition metals are highly active to hydrocarbon conversion. The dry reforming of methane (DRM) is a promising reaction because it converts methane and carbon dioxide into a "synthesis gas", or syngas, which can be processed to produce fuels and other value-added chemicals. When in the form of a nanoparticle supported on metal oxide, the active surface area of the metal is maximized, and less metal is required for catalysis. However, nanoparticle catalysts are readily deactivated by coking (carbon deposits) and sintering (nanoparticle agglomeration). Noble metals are highly active to DRM due to their high selectivity and resistance to deactivation, but they are typically too costly for practical use. Nickel is a promising DRM catalyst because of its low cost and high activity but is more susceptible to deactivation, therefore nickel is often paired with a second "promoter" metal to optimize the material and prevent deactivation. The development of active, stable bimetallic catalysts requires a detailed understanding of the chemistry at the surface during the reaction. In this work, we have identified the role of promoter sites using surface characterization techniques which provide better understanding of the catalytic mechanism.