Coupled Surface and Solid-State Charge and Ion Transport Dynamics at Mineral/Water Interfaces: Redox Transformation of the Iron Oxides
EMSL Project ID
39917
Abstract
This EMSL user proposal requests a continuation of EMSL access for a BES Geosciences supported project led by Dr. Rosso at PNNL. The past three years of research under this BES project we have been studying the interaction of Fe(II) with semiconducting Fe(III)-oxide minerals. This research has provided new insight into relationships between interfacial electron transfer processes, surface charge accumulation reactions, surface structure, and semiconducting properties of Fe(III)-oxides. Our EMSL-enabled experiments demonstrate a prospectively comprehensive model to explain the interplay among Fe(II) adsorption, interfacial electron transfer, bulk charge transport, and Fe(II) release (Yanina and Rosso, 2008). We have also invested significant effort into theory and simulation development, including seminal first principles calculations of electron transport at specific surfaces of Fe(III)-oxide crystals, and large-scale atomistic dynamics simulations of surface morphological evolution during dissolution.We propose to build on our findings using Fe(II) interaction with iron oxides as a model system for surface reactivity coupled to bulk transport processes. We will focus on determining the conditions and extent to which this coupling controls reductive dissolution and recrystallization of hematite, and the topotactic maghemite-magnetite transformation in the presence of aqueous Fe(II). The behavior of individual low-index crystal faces will be studied to closely link observations to fundamental aspects of site and surface structure. A combination of experiments and computational molecular simulations are proposed to develop a fundamental understanding of solution-dependent surface potential for directing crystallographic locations and the extent of Fe(II) adsorption, the kinetics of Fe(II)aq-Fe(III)oxide interfacial electron transfer, and the migration direction of injected electrons. Magnetite-maghemite transformation is a special case in which the diffusion of charge equivalents into or out of the solid may involve cation diffusion. We will attempt to develop large-scale dynamics simulations with an explicit representation of surface structure, bulk charge migration dynamics, and quantitative description of the surface potential for structurally specific oxide/solution interfaces. The proposed research is within the scope of the Geochemistry/Biogeochemistry and Subsurface Science EMSL theme, being closely aligned with sub-topical areas 'Linking molecular-scale processes to reactive transport' and 'Chemical and biological interactions at complex interfaces'.
Resources Requested: We request access to the ambient scanning probe microscopy laboratory in the EMSL building in room 1517 under the purview of the Environmental Spectroscopy and Biogeochemistry Facility to make use of the new Dimension Icon 'Geochemistry AFM' acquired under the American Recovery and Reinvestment Act. We request occasional access to the XRD laboratory, the electron microscopy laboratory (SEM/TEM), and the XPS laboratory. For computational resources, we request 150,000 node hours on Chinook and continued access to the SGI system 'Nwvisus' and the Linux cluster 'Spokane'. The request may be summarized as:
--Geochemistry AFM: 700 hrs/yr
--STM/AFM PicoSPM: 200 hrs/yr
--Pulsed Laser Deposition System: 40 hrs/yr
--Molecular Beam Epitaxy #1: 40 hrs/yr
--Dual FIB/SEM Electron Microscope: 20 hrs/yr
--Electron Microprobe: 10 hrs/yr
--Transmission Electron Microscope: 40 hrs/yr
--Quantum XPS: 40 hrs/yr
--Scanning Auger: 10 hrs/yr
--Chinook: 150,000 node hrs
--Spokane: unlimited access
--Nwvisus: unlimited access
Project Details
Project type
Large-Scale EMSL Research
Start Date
2010-10-01
End Date
2011-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Zarzycki PP, SME Chatman, T Preocanin, and KM Rosso. 2011. "Electrostatic Potential of Specific Mineral Faces." Langmuir 27(13):7986-7990. doi:10.1021/la201369g