Resolving Fe(II) Sorption and Oxidative Growth on Hematite (001

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Resolving Fe(II) Sorption and Oxidative Growth on Hematite (001) Using Atom Probe Tomography Sandra D. Taylor, Jia Liu, Bruce W. Arey, Daniel K. Schreiber, Daniel E. Perea, and Kevin Rosso J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b11989 • Publication Date (Web): 24 Jan 2018 Downloaded from http://pubs.acs.org on January 31, 2018

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The Journal of Physical Chemistry

Resolving Fe(II) Sorption and Oxidative Growth on Hematite (001) Using Atom Probe Tomography Sandra D. Taylor,* Jia Liu,+ Bruce W. Arey, Daniel K. Schreiber, Daniel E. Perea, Kevin M. Rosso* Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, U.S.A. +

Current address: Nanolab Technologies, 1708 McCarthy Blvd, Milpitas, CA 95035, U.S.A.

*To whom correspondence should be addressed: Sandra Taylor, [email protected], (509) 371-6374 Kevin Rosso, [email protected], (509) 371-6357

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ABSTRACT. The distribution of Fe resulting from the autocatalytic interaction of aqueous Fe(II) with the hematite (α-Fe2O3) (001) surface was directly mapped in three dimensions (3D) for the first time, using Fe isotopic labelling and atom probe tomography (APT). Micron-sized hematite platelets were reacted with aqueous Fe(II) enriched in 57Fe and prepared for APT using conventional FIB lift-out techniques. Mass spectrum analyses show that specific Fe-ionic species (i.e., Fe++ and FeO+) accurately reproduce isotopic ratios within natural abundance in the hematite bulk, and thus were utilized to characterize the distribution of 57Fe and quantify Fe isotopic concentrations. 3D reconstructions of Fe isotopic positions along the surface normal direction showed a zone enriched in 57Fe, consistent with oxidative adsorption of Fe(II) and growth at the relict hematite surface reacted with 57Fe(II)aq. An average net adsorption of 3.2 – 4.3 57Fe atoms nm–2 was estimated using Gibbsian interfacial excess principles. Statistical, gridbased frequency distribution analyses show a heterogeneous, non-random distribution of 57Fe across the surface, consistent with Volmer-Weber-like island growth. The unique 3D nature of the APT data provides an unprecedented means to quantify the atomic-scale distribution of sorbed 57Fe atoms and the extent of atomic segregation on the hematite surface. This new ability to spatially map growth on single crystal faces will enable resolution of long-standing unanswered questions about underlying mechanisms for electron and atom exchange involved in redox-catalyzed processes at this archetypal and broadly relevant interface.


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INTRODUCTION Fe(III)-oxides such as hematite and goethite are abundant in natural systems and are being developed into cost-effective (photo)catalytic substrates for energy conversion devices.1-2 In contact with water, the redox potential plays a commanding role in determining the structure and chemical behavior at the Fe(II)-Fe(III) oxide interface. The interconversion between surface Fe(III) (which is stable in the oxide) to Fe(II) (relatively stable in solution), and vice versa, is fundamental. In particular, under anoxic conditions or when cathodically biased, the system redox potential is poised such that both oxidation states can be present. This can in turn facilitate electron transfer and atom exchange reactions (described below), making the Fe(II)-Fe(III) oxide interface uniquely dynamic. For example, enhanced redox reaction rates are observed for organic3-7 and inorganic8-10 contaminants in these systems. Formation of Fe(II)-Fe(III) mixed valence surface phases can occur or the Fe(II)(aq)-Fe(III)-oxide interface can remain “sharp”, yet still undergo relatively rapid Fe atom exchange.11-12 In soils and sediments, microbial respiration enables these dynamical interfacial conditions.13-14 In electrochemical systems, Fe(II)(aq) is created when the applied potential exceeds that needed for reductive dissolution of the Fe(III)oxide. Thus, a substantial amount of experimental and theoretical work is underway to understand atom and electron exchange processes at Fe(II)(aq)-Fe(III) oxide interfaces in microscopic detail. When Fe(II)(aq) is in contact with a Fe(III)-oxide, the most conspicuous but daunting experimental challenge has been quantifying the flux of Fe atoms across the interface, as Fe(II)/Fe(III) can swap identities by electron transfer. That is, Fe(II) in the solution phase can adsorb onto a Fe(III)-oxide surface, such as that belonging to hematite (α-Fe2O3) and transfer its electron to an adjacent Fe(III) in the lattice. Electrons can potentially be conducted through the 3 ACS Paragon Plus Environment


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surface/bulk in specific crystallographic directions, ultimately leading to the reductive dissolution and release of Fe from elsewhere from the solid. Evidence for electron transfer at the surface has come from 57Fe Mössbauer spectroscopy analyses on Fe(III)-oxides (comprised predominantly of 56Fe) reacted with 57Fe(II)aq.3, 15 The measurements suggest that the amount of electron transfer at the interface depends on the average surface density of sorbed Fe(II), as Fe(II) oxidizes and forms a surface phase similar to the underlying oxide at coverages below a monolayer while a mixed Fe(II)-Fe(III) phase forms at higher coverages.15 Analytical mass spectrometry complements these measurements and provides evidence of atom exchange occurring; i.e., experiments that contact 57Fe(II)aq or 55Fe(II)aq with Fe(III)-oxides show that the Fe(II)aq becomes enriched in 56Fe in a matter of days while the solid becomes enriched in the tracer isotope, without substantial change in solid phase, mass, or physical characteristics.16-19 Rapid recrystallization of the solid is implied, nominally enabled by solid-state electron conduction through crystallites linking Fe(II) oxidative adsorption to its spatially distinct reductive release.11-12 The interaction of Fe(II) with individual oriented crystal faces available on large hematite single crystals has been probed using surface-sensitive spectroscopies, providing insight into Fe sorption and electron transfer mechanisms. Measurements using second harmonic generation,20 crystal truncation rod (CTR) diffractometry,21-22 and X-ray reflectivity (XR)23 all appear to support the notion that Fe(II) oxidatively adsorbs to the surface in a quasi-homoepitaxial manner, yielding hematite growth. This is also consistent with related computational molecular simulations.24-28 Models fit to CTR21-22 and XR23 datasets also indicate that the (001) surface continues to be hematite-like but is modified following interaction with Fe(II). These techniques provide valuable information on the sorbed Fe structure based on indirect and averaged


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observations. Information on the local structure of the deposited surface film (e.g., the morphology and distribution at the surface) is however difficult to determine as these measurements are principally in the surface normal direction and require spatial averaging laterally over large regions of the interface. Microscopy can address this to some extent though it can suffer from ambiguous identification of the sorbed phases.17, 29 Thus, direct visualization and explicit characterization of the sorbed Fe and its location on Fe surfaces would aid in determining adatom sorption and growth mechanisms, though this has been a persistent scientific challenge. Studies investigating the 57Fe(II) interaction with 56Fe(III)-oxides macroscopically imply the existence of atom exchange fronts in crystallites (i.e., by monitoring the mass transfer of the 57

Fe tracer out of aqueous phase18-19 and the valence of the 57Fe reaction product15, 30), though

these fronts have yet to be identified. Conceptually the recrystallized regions would preserve a record of the solution’s Fe isotopic composition during the reaction, thus enabling identification of the exchange fronts in these experiments via isotopic contrast. That is, 57Fe/56Fe ratios would be expected to be highest near the particle surface and decay inward to natural abundance (NA) ratios in the remnants of the original particle interior. Such a record could also contain information on crystallographic sites and directions where atom exchange occurs preferentially, providing insight into interfacial structure effects. Knowledge of these atom exchange fronts are critical to being able to follow the prospectively separate atom and electron exchange pathways that underlie the dynamics at the Fe(II)-Fe(III) oxide interface. However, because batch tracer experiments have had to rely on high surface area micro- and nanoparticles, there are very few mass dependent probes capable of the high spatial resolution necessary to explore the front



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directly in individual crystallites and thus such a record of atom exchange remains elusive experimentally. Atom probe tomography (APT) is a powerful technique that can be used to directly probe atom exchange fronts at the atomic scale in three-dimensions (3D). For example, 3D APT can map the elemental and isotopic distributions of dopants in solids and at interfaces with subnanometer resolution.31-33 It has also been used in geochronology to reveal the existence of nanoclusters containing radiogenic elements like Pb in zircon and elemental isotopic ratios.34-35 Although its usefulness in characterizing relatively small mass-dependent fractionations at interfaces is limited by signal sensitivity, for enriched tracer studies where isotopic contrasts can, in principle, be made much larger, APT holds great promise.36-37 Here for the first time, we develop and apply APT as a microscopic probe of the elusive atom exchange front as implied from research on the 57Fe(II) interaction with 56Fe(III)-oxides.15, 18-19, 30

While APT as a mass spectrometric technique is not appropriate for resolving oxidation

states, it is unique in its ability to differentiate and visualize the spatial distribution of Fe isotopes in atomic detail in 3D. In our experiments we recreate aqueous 57Fe(II) tracer conditions for Fe atom exchange with hematite (at natural Fe isotopic abundance) and directly probe the resulting distribution of 57Fe at the atom exchange reaction front in 3D using APT. To accomplish this goal, specimen preparation obstacles at the nanoscale first had to be overcome, and the performance of the APT technique for providing quantitative information had to be benchmarked. Therefore, the aims of this study were two-fold: (1) assess the applicability of APT in analyzing isotopically-enriched surfaces and (2) deepen insight into the interaction between sorbed Fe(II) on hematite, by characterizing the resulting 57Fe distribution in 3D at the interface for the first time. Hematite is an ideal candidate material because micron-sized euhedral


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crystallites are straightforward to synthesize, interpret in terms of crystallography, and nanoengineer into APT samples. The (001) surface was specifically analyzed because it is a key reactive interface with Fe(II) and its interaction with Fe(II) has been studied using the bespoken surface-sensitive spectroscopies and X-ray scattering methods. The results from this study provide new insight into the 3D nature of Fe redox interactions on the hematite basal surface, applicable to a broad range of research and development objectives focused on Fe oxide-water interfaces.



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METHODS Batch Experiments. Our study is based on reacting micron-sized hematite platelets with NA Fe isotope ratios with aqueous Fe(II) enriched in 57Fe. Euhedral, tabular, single crystal platelets of hematite were synthesized using a hydrothermal technique as described by Sapieszko and Matijevic 38. More specifically, hematite platelets were precipitated from a solution initially 0.04 M ferric nitrate, 0.2 M triethanolamine, 1.0 M sodium hydroxide, and 1.2 M sodium acetate. All chemicals were of reagent grade quality and first prepared to the above concentrations in separate plastic containers. The solution was hydrothermally aged and mixed in Parr reaction bombs (Parr Instrument Company, Moline, IL) in a mechanical convection oven (Blue M Model OV-472A-2, retrofitted with a rotisserie system) preheated to 250 °C for 2.5 hours. The reactors were then cooled in an ice bath and the precipitates were separated via centrifugation. The solids were also centrifuged and washed in ultrapure Milli-Q® water (typically 18.2 MΩ cm at 25 °C) three times, and finally dried in an oven at 70°C. This procedure yields hematite platelets that are generally ~2 – 20 µm in diameter and ~1 – 4 µm thick. The (001) surface is the dominant exposed face, truncated by (012) edge surfaces. Phase purity was confirmed with X-ray diffraction. The specific surface area (SSA) of the hematite particles was measured to be 0.2 m2 g–1 using the Brunauer-Emmett-Teller method with N2 adsorption and a degas temperature of 100 °C. Batch 57Fe(II) reaction experiments with loose powders of the platelets were conducted similar to that done by Larese-Casanova and Scherer 15. The 0.8 M 57Fe(II) stock solution was prepared by first dissolving 57Fe metal (Cambridge Isotopes) in 5 M HCl, filtering it through a 0.22 µm membrane, and diluting it to 0.1 M HCl. The 57Fe metal had a reported isotopic abundance of 95.93% 57Fe (compared to a NA value of 2.12%), which was confirmed by 8 ACS Paragon Plus Environment

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inductively-coupled mass spectrometry. A particle loading of 200 g L–1 hematite was used to obtain a surface loading of 40 m2 L–1. Hematite was reacted in high density polyethylene bottles at room temperature in a pH 7.5 solution (25 mM KBr, 25 mM HEPES buffer) in the absence (a control sample referred to as the “unreacted hematite” sample hereon) and presence (“reacted hematite”) of 2 mM 57Fe(II) for 24 hours. All experiments were conducted in an anoxic glovebox (N2/H2 atmosphere) to avoid Fe(II) oxidation by ambient oxygen. All solutions used for the Fe(II)-hematite reaction were mixed using anoxic, degassed water. The water was prepared by boiling ultrapure Milli-Q® water in Pyrex Corning® glass bottles on a hot plate for ~30 minutes under vacuum. Afterward the water was immediately transferred into the anoxic glove box where purified N2 was blown onto and sparged into it overnight. Following reaction the aqueous and solid fractions were separated via centrifugation. The supernatant was removed and analyzed with the ferrozine method (using a wavelength of 562 nm on a UV-Vis spectrophotometer) to determine the amount of Fe(II) remaining in solution, [Fe(II)aq]. Weakly bound Fe on the hematite surface was removed by first rinsing and centrifuging the powders with water once and then exposing them to a 0.4 M HCl (trace metal basis) solution for 10 minutes. The supernatant from this extraction was also analyzed to determine [Fe(II)extr], a quantity used to estimate the amount of 57Fe adsorbed to the powders according to Eqn. 1: [Fesorb] = [Fe(II)aq, initial] – [Fe(II)aq, final] – [Fe(II)extr, final]

(1)

Following the extraction step, the powders were rinsed and centrifuged with anoxic water. The washing procedure was found to effectively clean the surfaces of the hematite particles as ions from the solvent (e.g., K) could not be detected with APT. The unreacted and



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reacted hematite samples were then dried under N2 atmosphere and prepared for APT analyses. From this point, anoxia was no longer necessary to maintain. APT Specimen Preparation. As part of APT specimen preparation, the particles were dispersed onto Si wafers and coated with Cr first and then Ni (50 – 100 nm of each), using an ion beam sputter deposition system. These coatings protect the hematite surface, and provide a fiducial marker to identify the relative position of the particle surface, enabling this region to be placed at depth in the eventual APT tip. The Ni layer is used for imaging contrast during focused ion beam (FIB) milling while Cr was placed in direct contact with the hematite because it adheres well to Fe oxides and has a slightly lower but similar predicted evaporation field to Fe.39 Together these attributes facilitated a relatively smooth field evaporation from the protective capping layers into the Fe oxide during APT measurement. As discussed shortly, isobaric interferences at the interface exist from 54Cr and 54Fe species though these were systematically deconvoluted from one another. One of the advantages and reasons for working with the micron-size particles in this study was to utilize conventional FIB milling and lift-out techniques for APT specimen preparation. Following Cr-Ni deposition, individual particles with well-defined (001) basal surfaces were selected for APT analyses using scanning electron microscopy (SEM; FEI Helios Nanolab). A protective Pt capping layer was deposited on a rectangular section of the basal surface (e.g., ~3 × ~20 µm) by ion-beam induced deposition using the dual-beam FIB microscope, further protecting the Cr/Fe2O3 interface from damage and Ga contamination during ion milling. A lamellar wedge (~20 µm long) was created by trench milling on both sides with the ion beam (Ga+ ion, 30 kV) and was extracted with the Omniprobe micromanipulator. The lamellar wedge lift-out contained enough material to make several APT tips (e.g., 2 – 3), each


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representing a different region on the basal surface of a single particle. In this study, detailed results for both an unreacted and reacted APT specimens are provided and discussed, though we note here consistent reproducibility in APT results among several tips from a single particle. Thus, sections of the wedge were mounted over several Si microposts, and the sections were annular milled to obtain needle-shaped APT specimens with 4.0 at. %). A calculated Pearson coefficient µ was used to compare the relative strength of randomness (Eqn. 5; see Methods).39, 43-44 If µ=0 the distribution is completely random while if µ=1 the distribution is non-random and there is some spatial association between atoms. Serving as a reference value, µ for the experimental distribution of 57Fe at unreacted surfaces and in the bulk hematite region was calculated to be within 0.2 – 0.3. This indicates 57Fe atoms can be


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weakly correlated in the reconstruction although the distribution in these regions is still largely random as expected because the bulk crystal contains a natural distribution of Fe isotopes. In comparison, µ for the 57Fe distributed at the reacted hematite surfaces ranges from 0.6 to 0.8, indicating that the 57Fe atoms are more strongly associated with one another relative to that observed in the unreacted bulk regions and that the distribution of 57Fe within the deposited film is largely non-random. These deviations from randomness thus establish the incidence of atom segregation and formation of nanostructured surface texture at the reacted 57Fe-hematite interface. The ability of APT to visualize and quantify nanoscale segregation effects in 3D provides novel insights for materials processes such as crystal growth. Our APT measurements are in general agreement with the above-mentioned speculation from XR, and more specifically show that the lateral distribution of 57Fe sorbed onto the surface is heterogeneous and that nanoscale regions of multilayer deposition exist. The more concentrated regions can indicate local islandlike deposition, consistent with one interpretation from the XR study and other experimental studies that examined growth of hematite thin-films on different substrates like corundum and Si. These observations also suggest that the adsorption and growth of Fe on the hematite (001) surface at the present reaction conditions would occur via Volmer-Weber-like mechanisms, where adatom interactions with one another are stronger than interactions between adatoms and atoms at the surface. Nucleation of these islands conceptually could occur at energetically favorable sites such as kink, step, or other surface defect sites.50 Future Work to Advance Knowledge of Atom Exchange Fronts. Determining the amount of atom exchange that occurs in an absolute sense depends on the ability to locate the original interface, as mentioned above. Techniques such as XR rely on detecting differences in



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the structure with depth in the near-surface region to infer the location of the original hematite surface, although in the absence of structural contrast it cannot unambiguously distinguish between growth and dissolution. In contrast to XR, the use of tracer isotopes and APT enables us to track the Fe(II) reactant phase, clearly identifying 57Fe-enriched regions on the basal surface and deduce that net deposition occurs. Furthermore, the APT approach can resolve when isotope concentrations are statistically indistinguishable from NA and thus can generally indicate a horizon at depth that was at one time in contact with aqueous solution. For instance, this relict interface in the reacted specimen is at the onset where the Fe isotope concentrations are consistent with that observed within the bulk (Figure 4d, denoted to be at ~2 nm). However, for the experiments in this study, because the enrichment zone is so thin and appears to be consistent with the amount of Fe deposition expected based on solution measurements, the amount of atom exchange that may have occurred during oxidative adsorption of 57Fe(II), though unlikely, remains below the resolution of the APT method. Future work using the APT approach for understanding atom exchange processes in the Fe(II)-catalyzed recrystallization of Fe(III)-(oxyhydr)oxides should explore two possible methodological improvements. The first entails the prospect of developing inert fiducial markers for the original surface. Sub-monolayer coverage prior to reaction with a chemically distinct species nominally devoid of isobaric and/or polyatomic interferences with Fe ionic species (e.g., W or Au) could serve as a reference marker for the original surface location, assuming that surface undergoes net deposition and burial of the marker. An alternative idea is to embed a reference marker within the particle bulk at a known distance from the hematite surface. For instance, conceptually one could synthesize a hematite core bearing a minor element dopant like W, over top of which would be grown pure hematite of a known thickness. For example, doped


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particles could be coated with an epitaxially-grown hematite phase using techniques such as atomic layer deposition20 or molecular beam epitaxy.51-52 In either case, after fiducial marking, and after reaction with 57Fe(II)aq, changes in the isotopic composition of the hematite interface could then be referenced to a fixed known horizon at depth. Aspects of this marking approach that are not ideal include the possibility of altering the chemistry of the surface or the behavior of the atom exchange process itself. Thorough validation of the marking strategy itself would, of course, be required. The second possible advance is to explore systems and conditions where atom exchange is more extensive. In the hematite system, more extensive recrystallization could occur by increasing the surface-to-volume ratio (i.e., smaller particle sizes) and equilibration time. Analysis of other more reactive phases such as goethite is also potentially advantageous, as goethite has been shown to undergo more extensive atom exchange relative to hematite for equivalent conditions, though this material is restricted to small particle sizes. For instance, goethite nanoparticles have been found to undergo up to ~90% Fe atom exchange with 57Fe(II)aq over 30 days.12, 19 With this amount of atom exchange, it is possible that significant and crystallographically distinct isotopic gradient signatures (as described earlier) can be identified with APT. Analysis of nanoparticles may also provide the unique opportunity to observe atom exchange fronts approaching from opposite sides of a single crystallite and to infer linked surface reactivity across the entire particle. However, APT analysis of individual nanoparticles is far more challenging, particularly when aspiring to gain control of crystallographic orientation, and requires novel specimen preparation techniques such as careful nanomanipulation of particles (e.g., lifting out single nanoparticles and mounting them on microposts), embedding them in a material compatible with field ionization of the particle(s) of interest (free of voids and strongly-



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adhered and non-interfering ions),32, 53 and/or highly-controlled growth conditions (e.g., highly oriented, epitaxial growth of nanowires on APT Si-posts).54-56 Specimen preparation techniques enabling analysis of nanoparticles are currently being developed. Visualization of the oxidative adsorption of Fe(II) atoms onto Fe-oxide surfaces has been a persistent scientific challenge. In this study we were able to unambiguously image and quantify Fe atoms adsorbed onto the hematite (001) surface as well as successfully demonstrate that 57Fe can be utilized to track in situ reactions for Fe-materials with 3D APT. The novelty of imaging isotopic tracers with 3D APT suggests a new path forward for challenging problems such as investigating crystal growth occurring via self-adsorption and autocatalytic processes. More so, the described methodology can be adopted to study atom transport and exchange reactions across a broad range of materials and surfaces. For instance, it can be applied to provide new quantitative insights into the role of nanoscale defects on material degradation. Isotopic tracers have long been used to investigate reaction sites and elemental diffusivities during corrosion or oxidation of many materials.57-61 A 1D depth profiling technique (e.g., secondary ion mass spectrometry) is also often used to document the incorporation of the tracer isotopes in specific layers and interfaces. In the case of metal oxidation and corrosion, surfaces and grain boundaries are expected to be fast diffusion pathways at moderate temperatures (~300°C), establishing the rate-limiting process for further material degradation.62 Porous channels through alteration products are similarly predicted to facilitate the slow corrosion of borosilicate glass.63 To date, the reactions at these sites are have been impossible to directly image by conventional approaches. APT techniques using unique tracers, such as isotopic enrichment in the corroding medium, can be utilized to probe corrosion and diffusion reactions in these systems and across a


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broad range of materials classes. In turn, reaction mechanisms can be inferred and utilized to develop new reaction models. Further development of APT techniques using isotopic tracers will be valuable to describe these atom exchange and transport reaction mechanisms across different materials, given that it is the only method capable of directly imaging and quantifying isotopically-tagged reaction fronts in 3D at the nanoscale. It will be important to choose tracers such that there are minimal isobaric and/or polyatomic interferences. For instance, the presence of a hydride species (e.g., 56FeH) affects quantification of the 57Fe tracer and leads to erroneous interpretations of 57

Fe-enrichment. This issue could be overcome by utilizing another unique isotopic tracer, such

as 54Fe. Additionally, systematic analyses of samples from a given reaction would also aid in interpreting reaction mechanisms. For instance, by comparing the isotopic evolution across unreacted and reacted hematite surfaces we were able to deduce the reacted surface had not experienced extensive atom exchange. Similarly, surfaces that have undergone atom exchange (based on wet chemical measurements) will likely need to be compared to those that have not undergone exchange and/or those that have experienced varying extents of exchange for accurate and reliable characterization. Thus the viability of using APT and unique isotopic tracers to probe atom exchange and transport across a broad range of materials will require careful assessment, but holds great promise.

CONCLUSIONS Here we probed the autocatalytic interaction of aqueous Fe(II) with the hematite (001) surface using APT in an effort to identify and characterize reaction fronts in 3D space at the nanoscale 33 ACS Paragon Plus Environment


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and to also assess APT as a means to probe elusive atom exchange fronts resulting from the interconversion of Fe(II)aq at Fe(III)-oxide surfaces. Micron-sized hematite platelets with NA Fe isotope ratios were reacted with aqueous Fe(II) enriched in 57Fe and prepared for APT using conventional FIB lift-out techniques. 3D reconstructions of the Fe isotope positions and proxigrams of their concentrations along the surface normal direction provide unambiguous evidence for 57Fe adsorption and growth on the hematite (001) surface. Further analyses of the Fe isotopic concentrations at the surface enables us to determine that extensive atom exchange or recrystallization does not occur at the given experimental conditions. IE calculations predict a net oxidative adsorption of 3.2 – 4.3 57Fe atoms nm–2 on average, consistent with wet chemical observations and measurements from previous studies using surface-sensitive spectroscopies and X-ray scattering methods.15, 23 The mechanism by which the (001) surface grows is also deduced to occur via Volmer-Weber-like island growth; i.e., the mapped spatial distribution of 57Fe on the surface with respect to concentration highlights atomic segregation and clustering while statistical grid-based frequency distribution analyses confirm a heterogeneous, non-random distribution of oxidized Fe on the (001) surface. The unique 3D nature of the APT data provides an unprecedented means to quantify and image the atomic-scale distribution of sorbed 57Fe atoms on the hematite surface, providing valuable information on how sorbed Fe accumulates. We also successfully demonstrate that 57Fe can be utilized to track and visualize in situ reactions for Fe-materials with APT. This methodology can also be applied to study crystal growth as well as atom exchange and transport reactions in systems well beyond the geosciences. Collectively our observations show the promise of this technique to provide direct evidence of atom exchange processes that appear to underlie mineral recrystallization. That is, APT can provide a quantitative understanding of the


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isotopic composition at distinct sites/surfaces of recrystallized solids, where isotope concentration profiles from the recrystallized phase into the core substrate can be used to assess the existence of atom exchange fronts. The potential significance of this technique to this field is thus both timely and unique.

Acknowledgements This material is based upon work supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences (CSGB) Division through its Geosciences program at Pacific Northwest National Laboratory (PNNL). DKS acknowledges support from DOE-BES Materials Sciences and Engineering Division for assisting with APT experimental design, data interpretation, and manuscript preparation. Sample preparation and LEAP 4000 XHR analyses were performed using EMSL, a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research and located at PNNL. We would like to thank Shari Li for the BET measurements of the particles and Andrey V. Liyu for writing the randomization code.



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REFERENCES 1.

Sivula, K.; Le Formal, F.; Gratzel, M. Solar Water Splitting: Progress Using Hematite (α-

Fe2O3) Photoelectrodes. Chemsuschem 2011, 4, 432-449. 2.

Wheeler, D. A.; Wang, G. M.; Ling, Y. C.; Li, Y.; Zhang, J. Z. Nanostructured Hematite:

Synthesis, Characterization, Charge Carrier Dynamics, and Photoelectrochemical Properties. Energ. Environ. Sci. 2012, 5, 6682-6702. 3.

Williams, A. G. B.; Scherer, M. M. Spectroscopic Evidence for Fe(II)-Fe(III) Electron

Transfer at the Iron Oxide-Water Interface. Environ. Sci. Technol. 2004, 38, 4782-4790. 4.

Amonette, J. E.; Workman, D. J.; Kennedy, D. W.; Fruchter, J. S.; Gorby, Y. A.

Dechlorination of Carbon Tetrachloride by Fe(II) Associated with Goethite. Environ. Sci. Technol. 2000, 34, 4606-4613. 5.

Strathmann, T. J.; Stone, A. T. Mineral Surface Catalysis of Reactions Between FeII and

Oxime Carbamate pesticides. Geochim. et Cosmochim. Acta 2003, 67, 2775-2791. 6.

Chun, C. L.; Penn, R. L.; Arnold, W. A. Kinetic and Microscopic Studies of Reductive

Transformations of Organic Contaminants on Goethite. Environ. Sci. Technol. 2006, 40, 32993304. 7.

Charlet, L.; Silvester, E.; Liger, E. N-Compound Reduction and Actinide Immobilisation in

Surficial Fluids by Fe(II): The Surface FeIIIOFeIIOH° Species, as Major Reductant. Chem. Geol. 1998, 151, 85-93. 8.

Liger, E.; Charlet, L.; Van Cappellen, P. Surface Catalysis of Uranium(VI) Reduction by

Iron(II). Geochim. et Cosmochim. Acta 1999, 63, 2939-2955.


Page 37 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9.

Peretyazhko, T.; Zachara, J. M.; Heald, S. M.; Jeon, B. H.; Kukkadapu, R. K.; Liu, C.;

Moore, D.; Resch, C. T. Heterogeneous Reduction of Tc(VII) by Fe(II) at the Solid-Water Interface. Geochim. et Cosmochim. Acta 2008, 72, 1521-1539. 10.

Eary, L. E.; Rai, D. Kinetics of Chromate Reduction by Ferrous-Ions Derived from

Hematite and Biotite at 25°C. Am. J. Sci. 1989, 289, 180-213. 11.

Yanina, S. V.; Rosso, K. M. Linked Reactivity at Mineral-Water Interfaces Through Bulk

Crystal Conduction. Science 2008, 320, 218-222. 12.

Handler, R. M.; Beard, B. L.; Johnson, C. M.; Scherer, M. M. Atom Exchange between

Aqueous Fe(II) and Goethite: An Fe Isotope Tracer Study. Environ. Sci. Technol. 2009, 43, 11021107. 13.

Lovley, D. R. Dissimilatory Fe(III) and Mn(IV) Reduction. Microbiol. Revs. 1991, 55, 259-

287. 14.

Weber, K. A.; Achenbach, L. A.; Coates, J. D. Microorganisms Pumping Iron: Anaerobic

Microbial Iron Oxidation and Reduction. Nat. Rev. Microbiol. 2006, 4, 752-764. 15.

Larese-Casanova, P.; Scherer, M. M. Fe(II) Sorption on Hematite: New Insights Based on

Spectroscopic Measurements. Environ. Sci. Technol. 2007, 41, 471-477. 16.

Gorski, C. A.; Fantle, M. S. Stable Mineral Recrystallization in Low Temperature Aqueous

Systems: A Critical Review. Geochim. et Cosmochim. Acta 2017, 198, 439-465. 17.

Joshi, P.; Gorski, C. A. Anisotropic Morphological Changes in Goethite during Fe2+-

Catalyzed Recrystallization. Environ. Sci. Technol. 2016, 50, 7315-7324.



18.

Page 38 of 44

Frierdich, A. J.; Helgeson, M.; Liu, C. S.; Wang, C. M.; Rosso, K. M.; Scherer, M. M. Iron

Atom Exchange between Hematite and Aqueous Fe(II). Environ. Sci. Technol. 2015, 49, 84798486. 19.

Handler, R. M.; Frierdich, A. J.; Johnson, C. M.; Rosso, K. M.; Beard, B. L. Wang, C.; Latta,

D. E.; Neumann, A.; Pasakarnis, T.; Premaraine, W. A. P.; et al. Fe(II)-Catalyzed Recrystallization of Goethite Revisited. Environ. Sci. Technol. 2014, 48, 11302-11311. 20.

Jordan, D. S.; Hull, C. J.; Troiano, J. M.; Riha, S. C.; Martinson, A. B. F.; Rosso, K. M.;

Geiger, F. M. Second Harmonic Generation Studies of Fe(II) Interactions with Hematite (αFe2O3). J. Phys. Chem. C 2013, 117, 4040-4047. 21.

Tanwar, K. S.; Petitto, S. C.; Ghose, S. K.; Eng, P. J.; Trainor, T. P. Fe(II) Adsorption on

Hematite (0001). Geochim. et Cosmochim. Acta 2009, 73, 4346-4365. 22.

Tanwar, K. S.; Petitto, S. C.; Ghose, S. K.; Eng, P. J.; Trainor, T. P. Structural Study of Fe(II)

Adsorption on Hematite (11 ̅02). Geochim. et Cosmochim. Acta 2008, 72, 3311-3325. 23.

Catalano, J. G.; Fenter, P.; Park, C.; Zhang, Z.; Rosso, K. M. Structure and Oxidation State

of Hematite Surfaces Reacted with Aqueous Fe(II) at Acidic and Neutral pH. Geochim. et Cosmochim. Acta 2010, 74, 1498-1512. 24.

Russell, B.; Payne, M.; Ciacchi, L. C. Density Functional Theory Study of Fe(II) Adsorption

and Oxidation on Goethite Surfaces. Phys. Rev. B 2009, 79. 25.

Kerisit, S.; Zarzycki, P.; Rosso, K. M. Computational Molecular Simulation of the

Oxidative Adsorption of Ferrous Iron at the Hematite (001)-Water Interface. J. Phys. Chem. C 2015, 119, 9242-9252.


Page 39 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


26.

Taylor, S. D.; Marcano, M. C.; Becker, U. A First Principles Investigation of Electron

Transfer Between Fe(II) and U(VI) on Insulating Al- vs. Semiconducting Fe-oxide Surfaces via the Proximity Effect. Geochim. et Cosmochim. Acta 2017, 197, 305-322. 27.

Taylor, S. D.; Becker, U.; Rosso, K. M. Electron Transfer Pathways Facilitating U(VI)

Reduction by Fe(II) on Al- vs Fe-Oxides. J. Phys. Chem. C 2017, 121, 19887-19903. 28.

Zarzycki, P.; Rosso, K. M. Stochastic Simulation of Isotopic Exchange Mechanisms for

Fe(II)-Catalyzed Recrystallization of Goethite. Environ. Sci. Technol. 2017, 51, 7552-7559. 29.

Eggleston, C. M.; Stack, A. G.; Rosso, K. M.; Bice, A. M. Adatom Fe(III) on the Hematite

Surface: Observation of a Key Reactive Surface Species. Geochem. Trans. 2004, 5, 33-40. 30.

Larese-Casanova, P.; Kappler, A.; Haderlein, S. B. Heterogeneous Oxidation of Fe(II) on

Iron Oxides in Aqueous Systems: Identification and Controls of Fe(III) Product Formation. Geochim. et Cosmochim. Acta 2012, 91, 171-186. 31.

Sun, Z. Y.; Hazut, O.; Huang, B. C.; Chiu, Y. P.; Chang, C. S.; Yerushalmi, R.; Lauhon, L. J.;

Seidman, D. N. Dopant Diffusion and Activation in Silicon Nanowires Fabricated by Ex Situ Doping: A Correlative Study via Atom-Probe Tomography and Scanning Tunneling Spectroscopy. Nano Lett. 2016, 16, 4490-4500. 32.

Perea, D. E.; Liu, J.; Bartrand, J.; Dicken, Q.; Thevuthasan, S. T.; Browning, N. D.; Evans, J.

E. Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin. Sci. Rep. 2016, 6. 33.

Thompson, K.; Bunton, J. H.; Moore, J. S.; Jones, K. S. Compositional Analysis of Si

Nanostructures: SIMS-3D Tomographic Atom Probe Comparison. Semicond. Sci. Tech. 2007, 22, S127-S131.



34.

Page 40 of 44

Valley, J. W.; Cavosie, A. J.; Ushikubo, T.; Reinhard, D. A.; Lawrence, D. F.; Larson, D.

J.; Clifton, P. H.; Kelly, T. F.; Wilde, S. A.; Moser, D. E.; et al. Hadean Age for a Post-MagmaOcean Zircon Confirmed by Atom-Probe Tomography. Nat. Geosci. 2014, 7, 219-223. 35.

Peterman, E. M.; Reddy, S. M.; Saxey, D. W.; Snoeyenbos, D. R.; Rickard, W. D.;

Fougerouse, D.; Kylander-Clark, A. R. Nanogeochronology of Discordant Zircon Measured by Atom Probe Microscopy of Pb-Enriched Dislocation Loops. Sci. Adv. 2016, 2, e1601318. 36.

Shimizu, Y.; Takamizawa, H.; Kawamura, Y.; Uematsu, M.; Toyama, T.; Inoue, K.; Haller,

E. E.; Itoh, K. M.; Nagai, Y. Atomic-Scale Characterization of Germanium Isotopic Multilayers by Atom Probe Tomography. J. Appl. Phys. 2013, 113. 37.

Moutanabbir, O.; Isheim, D.; Seidman, D. N.; Kawamura, Y.; Itoh, K. M. Ultraviolet-Laser

Atom-Probe Tomographic Three-Dimensional Atom-by-Atom Mapping of Isotopically Modulated Si Nanoscopic Layers. Appl. Phys. Lett. 2011, 98. 38.

Sapieszko, R. S.; Matijevic, E. Preparation of Well-Defined Colloidal Particles by Thermal-

Decomposition of Metal-Chelates. 1. Iron-Oxides. J. Colloid Interf. Sci. 1980, 74, 405-422. 39.

Miller, M. K.; Forbes, R. G. Atom-Probe Tomography: The Local Electrode Atom Probe;

Springer: New York, 2014. 40.

Hellman, O. C.; Vandenbroucke, J. A.; Rusing, J.; Isheim, D.; Seidman, D. N. Analysis of

Three-Dimensional Atom-Probe Data by the Proximity Histogram. Microsc. and Microanaly. 2000, 6, 437-444. 41.

Hellman, O. C.; Seidman, D. N. Measurement of the Gibbsian Interfacial Excess of Solute

At an Interface of Arbitrary Geometry Using Three-Dimensional Atom Probe Microscopy. Mat. Sci. Eng. A 2002, 327, 24-28.


Page 41 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


42.

Yoon, K. E.; Noebe, R. D.; Hellman, O. C.; Seidman, D. N. Dependence of Interfacial

Excess on the Threshold Value of the Isoconcentration Surface. Surf. Interface Anal. 2004, 36, 594-597. 43.

Moody, M. P.; Stephenson, L. T.; Ceguerra, A. V.; Ringer, S. P. Quantitative Binomial

Distribution Analyses of Nanoscale Like-Solute Atom Clustering and Segregation in Atom Probe Tomography Data. Microsc. Res. Techniq. 2008, 71, 542-550. 44.

Perea, D. E.; Arslan, I.; Liu, J.; Ristanovic, Z.; Kovarik, L.; Arey, B. W.; Lercher, J. A.; Bare,

S. R.; Weckhuysen, B. M. Determining the Location and Nearest Neighbours of Aluminium in Zeolites with Atom Probe Tomography. Nat. Commun. 2015, 6. 45.

Pedersen, H. D.; Postma, D.; Jakobsen, R.; Larsen, O. Fast Transformation of Iron

Oxyhydroxides by the Catalytic Action of Aqueous Fe(II). Geochim. et Cosmochim. Acta 2005, 69, 3967-3977. 46.

Sabioni, A. C. S.; Daniel, A. M. J. M.; Macedo, W. A. A.; Martins, M. D.; Huntz, A. M.;

Jomard, F.; Persiano, A. I. C. First Study of Iron Self-Diffusion in Fe2O3 Single Crystals by SIMS. Defect Diffus. Forum 2005, 237-240, 277-281. 47.

Sabioni, A. C. S.; Huntz, A. M.; Daniel, A. M. J. M.; Macedo, W. A. A. Measurement of

Iron Self-Diffusion in Hematite Single Crystals by Secondary Ion-Mass Spectrometry (SIMS) and Comparison with Cation Self-Diffusion in Corundum-Structure Oxides. Philos. Mag. 2005, 85, 3643-3658. 48.

Marquis, E. A.; Geiser, B. P.; Prosa, T. J.; Larson, D. J. Evolution of Tip Shape During Field

Evaporation of Complex Multilayer Structures. J. Microsc. 2011, 241, 225-233.



49.

Page 42 of 44

Larson, D. J.; Gault, B.; Geiser, B. P.; De Geuser, F.; Vurpillot, F. Atom Probe Tomography

Spatial Reconstruction: Status and Directions. Curr. Opin. Solid. St. Mat. Sci. 2013, 17, 236-247. 50.

Kitamura, M.; Hosoya, S.; Sunagawa, I. Reinvestigation of the Re-Entrant Corner Effect in

Twinned Crystals. J. Cryst. Growth 1979, 47, 93-99. 51.

Gota, S.; Guiot, E.; Henriot, M.; Gautier-Soyer, M. Atomic-Oxygen-Assisted MBE Growth

of α-Fe2O3 on α-Al2O3 (0001): Metastable FeO (111)-Like Phase at Subnanometer Thicknesses. Phys. Rev. B 1999, 60, 14387-14395. 52.

Kim, Y. J.; Gao, Y.; Chambers, S. A. Selective Growth and Characterization of Pure,

Epitaxial α-Fe2O3 (0001) and Fe3O4 (001) Films by Plasma-Assisted Molecular Beam Epitaxy. Surf. Sci. 1997, 371, 358-370. 53.

Larson, D. J.; Giddings, A. D.; Wu, Y.; Verheijen, M. A.; Prosa, T. J.; Roozeboom, F.; Rice,

K. P.; Kessels, W. M. M.; Geiser, B. P.; Kelly, T. F. Encapsulation Method for Atom Probe Tomography Analysis of Nanoparticles. Ultramicroscopy 2015, 159, 420-426. 54.

Perea, D. E.; Allen, J. E.; May, S. J.; Wessels, B. W.; Seidman, D. N.; Lauhon, L. J. Three-

Dimensional Nanoscale Composition Mapping of Semiconductor Nanowires. Nano Lett. 2006, 6, 181-185. 55.

Perea, D. E.; Lensch, J. L.; May, S. J.; Wessels, B. W.; Lauhon, L. J. Composition analysis of

single semiconductor nanowires using pulsed-laser atom probe tomography. Appl. Phys. A 2006, 85, 271-275. 56.

Blumtritt, H.; Isheim, D.; Senz, S.; Seidman, D. N.; Moutanabbir, O. Preparation of

Nanowire Specimens for Laser-Assisted Atom Probe Tomography. Nanotechnology 2014, 25.


Page 43 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


57.

Lobnig, R. E.; Schmidt, H. P.; Hennesen, K.; Grabke, H. J. Diffusion of Cations in Chromia

Layers Grown on Iron-Base Alloys. Oxid. Met. 1992, 37, 81-93. 58.

Pint, B. A.; Martin, J. R.; Hobbs, L. W. 18O/SIMS Characterization of the Growth-

Mechanism of Doped and Undoped α-Al2O3. Oxid. Met. 1993, 39, 167-195. 59.

Valle, N.; Verney-Carron, A.; Sterpenich, J.; Libourel, G.; Deloule, E.; Jollivet, P. Elemental

and Isotopic (29Si and 18O) Tracing of Glass Alteration Mechanisms. Geochim. et Cosmochim. Acta 2010, 74, 3412-3431. 60.

Gin, S.; Jollivet, P.; Fournier, M.; Angeli, F.; Frugier, P.; Charpentier, T. Origin and

Consequences of Silicate Glass Passivation by Surface Layers. Nat. Commun. 2015, 6. 61.

Martin, T. L.; Coe, C.; Bagot, P. A. J.; Morrall, P.; Smith, G. D. W.; Scott, T.; Moody, M. P.

Atomic-Scale Studies of Uranium Oxidation and Corrosion by Water Vapour. Sci. Rep. 2016, 6. 62.

Scott, P. M.; Lecalvar, M. In Some Possible Mechanisms of Intergranular Stress-Corrosion

Cracking of Alloy-600 in Pwr Primary Water, Proceedings of the Sixth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, 1993; pp 657-667. 63.

Cailleteau, C.; Angeli, F.; Devreux, F.; Gin, S.; Jestin, J.; Jollivet, P.; Spalla, O. Insight into

Silicate-Glass Corrosion Mechanisms. Nat. Mater. 2008, 7, 978-983.



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Resolving Fe(II) Sorption and Oxidative Growth on Hematite (001

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