Direct Measurement of Electron Mobility in Carbon-Nanocatalyst Composites
Abstract
In this STIR project, we will demonstrate direct measurement of electron mobility in a carbon-nanocatalyst composite material as a proof-of-concept study. The Hall measurement will be used to measure electron mobility, and the well-characterized materials of graphene and iron nanoparticles will be studied. Hall measurement of electron mobility has been used to evaluate semiconductor materials and graphene but has only recently been demonstrated for individual nanostructures. To our knowledge, direct measurement of electron mobility has not been demonstrated for immobilized nanocatalysts used in aqueous environments (e.g., water treatment). The long-term goal of this research is to determine the mechanism(s) by which the support material (e.g., high surface area carbon) of an immobilized nanoparticle catalyst composite enhances nanocatalyst reactivity towards target water contaminants and extends nanocatalyst lifetime in an aqueous environment. It has been well-accepted in the water treatment field that high surface area materials, such as carbon, are highly effective, inert sorbents. These materials are also excellent supports for the immobilization of nanocatalysts and, as such, continue to be an intense focus of current research. However, there are several recent studies on carbon-iron nanoparticle composites that suggest that carbon may participate in catalytic degradation reactions of water contaminants. The primary mechanism is suggested to be through electron shuttling from reactive nanoparticles through the carbon to surface-adsorbed water contaminants such as trichloroethylene (TCE) (Fig. 1). In another set of studies, researchers have shown that an aluminum-based support material can greatly extend the lifetime of iron-based nanoparticle catalysts (from minutes to days), where it is suggested that electrons are shuttled from the aluminum support to the iron nanoparticle. In both cases, the electron shuttling mechanism is inferred through indirect measurements, such as contaminant degradation and dissolved cation concentrations (e.g., Fe2+ or Al3+). However, there is, as yet, no study that has attempted to directly measure electron transport and confirm the theory that electron shuttling is responsible for the observed enhanced reactivity and/or lifetime. This STIR project will demonstrate direct measurement of electron mobility in a model material, a graphene-iron nanoparticle composite, thereby laying the foundation for fundamental investigation of how support materials enable enhanced reactivity and lifetime of catalytic nanoparticles in water contaminant degradation scenarios. Ultimately, this research will enable the accelerated development and control of reactive, nanostructured catalysts that have realistic lifetimes in aqueous environments.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 04, 2018
- Source ID
- W911NF1610581
Entities
People
- Lauren F Greenlee
Organizations
- Army Contracting Command
- United States Army
- University of Arkansas