|Matranga, Christopher Shawn
A majority of the energy used in the US is derived from fossil fuels and recent forecasts suggest these fuels will continue to be a critical factor in the US energy portfolio for many decades to come. A primary benefit of fossil energy is that domestic sources, such as coal, provide a safe and stable source of fuel over foreign sources. In addition to combustion for power plant applications, coal can be converted directly into liquid fuels through the Fischer-Tropsch (FT) process, thus circumventing much of our reliance on foreign oil. The use of coal for domestic power generation and as a liquid fuel source presents us with some fascinating technical and scientific challenges. Some of these challenges include the development of next-generation catalysts for FT applications, as well as catalysts which can convert CO2 from the fuel combustion back into higher value products like alcohols or other organic species.
With these motivating factors in mind, there are several research projects currently in progress. One set of projects focuses on using classical surface science methodologies like scanning tunneling microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, ion scattering spectroscopy, low energy electron diffraction, and Auger electron spectroscopy to study single-crystal surfaces useful to FT and carbon capture applications. Materials of interest are iron and cobalt-based systems for FT studies, as well as TiO2 and other photo- and/or electro-catalysts, which can be used for the reduction of CO2. A large portion of this work focuses on the in situ growth of novel nanostructured catalysts on single-crystal substrates. The effects of size, shape, and defects on the reactivity of these materials are studied. Projects are also possible with fuel cell materials like Lanthanum Strontium Manganate (LSM) or Yittria-stabilized Zirconia (YSZ). A key piece of instrumentation for all of this work is a state-of-the-art ultrahigh vacuum surface science system that houses six distinct analytical methodologies, as well as evaporative growth capabilities.
Other projects focus on the study of novel nanocatalysts, which can be incorporated into traditional catalyst supports. One particular project focuses on using solution phase growth techniques for controlling the size and shape of metal catalyst particles in order to tailor reactivity and selectivity. In the case of a face centered cubic metal, a tetrahedral shaped catalyst particle will only have (111) facets exposed on its surface in comparison to a cube shaped particle, which will only have (100) facets. Simple surface science considerations tell us that each of these particles will have very different chemical reactivities. Some current topics of interest include studying the effects of residual surfactants from the synthesis step on the chemical reactivity of these particles. The shape and size dependent kinetics of simple model reactions like CO oxidation of these nanoctalysts are evaluated using infrared, Raman, and other analytical techniques. Application of size and shape controlled catalysis to photoreduction catalysts like TiO2 and fuel cell cathode materials like LSM and YSZ are also emerging topics. Key instrumentation includes in situ infrared and Raman spectrometers which allow us to probe mechanistic details of reactivity in real time. X-ray photoelectron spectroscopy instrumentation with an in situ reaction cell enhances our understanding of the reactivity of these nanocatalysts. Commercial chemisorption instrumentation allows for kinetic studies and general catalyst characterization.
Fossil fuels; Coal; Fischer-Tropsch; Carbon; YSZ; Surface science methodologies;