Variation in the iron oxidation states of magnetite nanocrystals as a function of crystallite size: The impact on electrochemical capacity

Menard, Melissa C.; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.

doi:10.1016/j.electacta.2013.02.012

Cited by 38 publications

(47 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The XANES spectra of the FGC and FG samples had very similar shapes to that of Fe 3 O 4 standard. The pre-edge features of the K -edge of transition metal compounds have been found to be affected by the oxidation state and coordination environment of the atom of interest 31–33 , which can be determined from the pre-edge position and the height of the peak 34 . The pre-edge position can thus be used to probe the average Fe-redox state 31 .…”

Section: Resultsmentioning

confidence: 99%

Hierarchical Fe3O4-reduced graphene oxide nanocomposite grown on NaCl crystals for triiodide reduction in dye-sensitized solar cells

Harnchana

Chaiyachad

Pimanpang

et al. 2019

Sci Rep

View full text Add to dashboard Cite

Cost-effective reduced graphene oxide sheets decorated with magnetite (Fe3O4) nanoparticles (Fe3O4-rGO) are successfully fabricated via a chemical vapor deposition (CVD) technique using iron (III) nitrate as an iron precursor, with glucose and CH4 as carbon sources, and NaCl as a supporting material. TEM analysis and Raman spectroscopy reveal hierarchical nanostructures of reduced graphene oxide (rGO) decorated with Fe3O4 nanoparticles. Fe K-edge x-ray absorption near edge structure (XANES) spectra confirm that the nanoparticles are Fe3O4 with a slight shift of the pre-edge peak position toward higher energy suggesting that the fabricated Fe3O4 nanoparticles have a higher average oxidation state than that of a standard Fe3O4 compound. The hierarchical Fe3O4-rGO is found to exhibit an excellent catalytic activity toward the reduction of triiodide to iodide in a dye-sensitized solar cell (DSSC) and can deliver a solar cell efficiency of 6.65%, which is superior to a Pt-based DSSC (6.37%).

show abstract

Section: Resultsmentioning

confidence: 99%

Hierarchical Fe3O4-reduced graphene oxide nanocomposite grown on NaCl crystals for triiodide reduction in dye-sensitized solar cells

Harnchana

Chaiyachad

Pimanpang

et al. 2019

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Until recently, the performance of 4 magnetite was limited by slow solid-state transport of lithium ions through the close-packed structure of the material. However, nanosizing has been utilized to shorten the path length for lithium ion diffusion, which has improved the rate capability and increased the utilization of the active material [13][14][15][25][26][27]. Further improvements in rate capability and utilization have been obtained using alternative electrode synthesis methods that reduce agglomeration of the nanocrystals [28,29].…”

Section: Introductionmentioning

confidence: 99%

Simulations of Lithium-Magnetite Electrodes Incorporating Phase Change

Knehr

Cama

Brady

et al. 2017

Electrochimica Acta

Self Cite

View full text Add to dashboard Cite

The phase changes occurring in magnetite (Fe 3 O 4 ) during lithiation and voltage recovery experiments are modeled using a model that simulates the electrochemical performance of a Fe 3 O 4 electrode by coupling the lithium transport in the agglomerate and nano-crystal lengthscales to thermodynamic and kinetic expressions. Phase changes are described using kinetic expressions based on the Avrami theory for nucleation and growth. Simulated results indicate that the slow, linear voltage change observed at long times during the voltage recovery experiments can be attributed to a slow phase change from α-Li x Fe 3 O 4 to β-Li 4 Fe 3 O 4 . In addition, the long voltage plateau at ~1.2 V observed during lithiation of electrodes is attributed to conversion from α-Li x Fe 3 O 4 to γ-(4 Li 2 O + 3 Fe). Simulations for the lithiation of 6 and 32 nm Fe 3 O 4 suggest the rate of conversion to γ-(4 Li 2 O + 3 Fe) decreases with decreasing crystal size.

show abstract

“…There are differences in the 10 nm versus the 30 nm crystallite size Fe 3 O 4 open‐circuit potential versus lithium at low depths of discharge ( x < 1.0), previously understood by variations in the concentration of Fe cationic defects as a function of crystallite size . However, on the first voltage plateau, the 10 and 30 nm Fe 3 O 4 nanocrystallites exhibit the same open circuit potential versus lithium, ≈1.8 V, illustrated in Figure S1 (Supporting Information).…”

Section: Resultsmentioning

confidence: 80%

The Systematic Refinement for the Phase Change and Conversion Reactions Arising from the Lithiation of Magnetite Nanocrystals

Lininger

Bruck

Lutz

et al. 2019

Adv Funct Materials

Self Cite

View full text Add to dashboard Cite

Nanostructured materials can exhibit phase change behavior that deviates from the macroscopic phase behavior. This is exemplified by the ambiguity for the equilibrium phases driving the first open-circuit voltage (OCV) plateau for the lithiation of Fe 3 O 4 nanocrystals. Adding complexity, the relaxed state for Li x Fe 3 O 4 is observed to be a function of electrochemical discharge rate. The phases occurring on the first OCV plateau for the lithiation of Fe 3 O 4 nanocrystals have been investigated with density functional theory (DFT) through the evaluation of stable, or hypothesized metastable, reaction pathways. Hypotheses are evaluated through the systematic combined refinement with X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) measurements, neutron-diffraction measurements, and the measured OCV on samples lithiated to x = 2.0, 3.0, and 4.0 in LixFe 3 O 4 . In contrast to the Li-Fe-O bulk phase thermodynamic pathway, Fe 0 is not observed as a product on the first OCV plateau for 10-45 nm nanocrystals. The phase most consistent with the systematic refinement is LiFe 3 O 4 , showing Li+Fe cation disorder. The observed equilibrium concentration for conversion to Fe 0 occurs at x = 4.0. These definitive phase identifications rely heavily on the systematic combined refinement approach, which is broadly applicable to other nanoand mesoscaled systems that have suffered from difficult or crystallite-sizedependent phase identification.

show abstract

Variation in the iron oxidation states of magnetite nanocrystals as a function of crystallite size: The impact on electrochemical capacity

Cited by 38 publications

References 39 publications

Hierarchical Fe3O4-reduced graphene oxide nanocomposite grown on NaCl crystals for triiodide reduction in dye-sensitized solar cells

Hierarchical Fe3O4-reduced graphene oxide nanocomposite grown on NaCl crystals for triiodide reduction in dye-sensitized solar cells

Simulations of Lithium-Magnetite Electrodes Incorporating Phase Change

The Systematic Refinement for the Phase Change and Conversion Reactions Arising from the Lithiation of Magnetite Nanocrystals

Contact Info

Product

Resources

About