Molecular Dynamics Study of Fe(II) Adsorption, Electron Exchange, and Mobility at Goethite (α-FeOOH) Surfaces

Journal Article · Thu Feb 12 04:00:00 EST 2015 · Journal of Physical Chemistry C, 119(6):3111-3123

DOI:https://doi.org/10.1021/jp511086r· OSTI ID:1184977

Zarzycki, Piotr P.; Kerisit, Sebastien N.; Rosso, Kevin M.

We present classical molecular simulations of the adsorption free energy profiles for the aqueous Fe(II) ion approaching key low index crystal faces of goethite at neutral surface charge conditions. Calculated profiles show minima corresponding to stable outer- and inner-sphere adsorbed structures. We analyzed the energetics and kinetics of most possible interfacial electron transfer reactions, as well as analyzing the same for subsurface migration pathways of injected electrons through calculating the Marcus free energy surfaces. We conclude that inner-sphere Fe(II)-complex formation is required for the interfacial electron transfer to occur, but the energetic cost of moving from the outer-sphere to inner-sphere geometry may prevent electron injection at some faces. We also show that some surfaces, especially (101), (100) and (001), are more energetically prone toward reduction than others. We demonstrate that subsurface charge migration in directions parallel to the surface, which run along the iron chains, is more energetically plausible than conduction through the resistive crystal bulk phase. Collectively this leads to the conclusion that Fe(II)-catalyzed recrystallization of goethite most likely proceeds by short path length electron migration through specific goethite surfaces along specific directions, until capture at Fe sites structurally susceptible to reduction and release.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1184977
• Report Number(s): PNNL-SA-109629; 47824; KC0302060
• Journal Information: Journal of Physical Chemistry C, 119(6):3111-3123, Journal Name: Journal of Physical Chemistry C, 119(6):3111-3123
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Environmental Molecular Sciences Laboratory