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Fe II-III (oxy)hydroxycarbonate green rusts; from ferri- to ferromagnetism

Fe II-III (oxy)hydroxycarbonate green rusts; from ferri- to ferromagnetism J.-M. R. Génin et al. Institut Jean Barriol Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564 CNRS- Université Henri Poincaré-Nancy 1, Département Matériaux et Structures, ESSTIN,

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Fe II-III (oxy)hydroxycarbonate green rusts; from ferri- to ferromagnetism

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  1. FeII-III (oxy)hydroxycarbonate green rusts; from ferri- to ferromagnetism J.-M. R. Génin et al. Institut Jean Barriol Laboratoire de Chimie Physique et Microbiologie pour l'Environnement,UMR 7564 CNRS-Université Henri Poincaré-Nancy 1, Département Matériaux et Structures, ESSTIN, 405 rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France. E-Mail:genin@lcpme.cnrs-nancy.fr “Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

  2. 100 98 96 94 92 D2 12% GR1(Cl-) x 0.33 D2 32% Transmission Mössbauer spectra measured at 78 K of various Green Rusts x = FeIII / Fetotal is obtained directly from the spectrum (RA of D3) It is alwaysfound that 0.25 < x < 0.33 D1 : FeII with no anion first nearest neighbour D2 : FeII with one anion first nearest neighbour GR1(CO32-)x = 0.25 D1 37% Transmittance % D3 26% D3 31% Transmittance % 78 K 78 K D1 62% (a) (b) 97 -4 -3 -2 -1 0 1 2 3 4 92 Velocity (mm s-1) 100 100 GR1(CO32-)x = 0.33 D2 15% 99 98 87 GR2(SO42-) x = 0.33 D3 34% 96 98 Transmittance % D3 34% Transmittance (%) D1 51% 97 94 82 78 K 78 K Velocity (mm s-1) D1 66% -4 -3 -2 -1 0 1 2 3 4 (d) (c) 92 96 95 90 94 88 Velocity (mm s-1) Velocity (mm s-1) -6 -4 -2 0 2 4 6 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 FeII-III hydroxysalts green rusts, which are layered double hydroxides (LDH), are constituted of [FeII(1-x) FeIIIx (OH)2 ]x+ layers and [(x/n)An- (mx/n)H2O]x- interlayers that can incorporate various anions such as Cl-, CO32-, SO42-, HCOO-, C2O42-, SeO42- …For ChlorideGR1(Cl-): [FeII2FeIII(OH)6]+[Cl-2H2O]-SulphateGR2(SO42-): [FeII4FeIII2(OH)12]2+[SO42-8H2O]2-Carbonate GR1(CO32-): [FeII4FeIII2(OH)12]2+[CO32-3H2O]2-There exist two types of space groups as determined by XRD: GR1 [R(-3)m] and GR2 [P(-3)m1] that depend on the shape of the anion. Mössbauer spectra display 2 ferrous doublets D1 & D2 (large D) and1 ferric doublet D3 (small D).

  3. OH- B OH- GR1(Cl-) GR1(CO32-) GR2(SO42-) c B OH- Fen+ 2.5 B c A Fen+ Stacking sequence at scale of the Fe cation layersGR1 [R(-3)m] and GR2 [P(-3)m1](a) Cl- anions and OH- layers of GR1(Cl-).(b) CO32- anion interlayers and OH- layers along the 3-fold axis of GR1(CO32-)(c) SO42- anion interlayers and OH- layers along the 3-fold axis of GR2(SO42-);A, B, C and a, b, c positions represent the sites in the hexagonal pavement of ions. c Fen+ OH- A A OH- 1 O2- in c & 3 O2- in ~ b OH- a Cl- O2- in ~ aC in b or c CO32- 2 SO42- OH- OH- A c nm 1 O2- in c & 3 O2- in ~ a A b Fen+ b Fen+ SO42- C C OH- 1.5 OH- OH- B c O2- in ~ c C in a or b Cl- c CO32- Fen+ OH- A OH- OH- C 1 O2- in c & 3 O2- in ~ b C 1 a a Fen+ Fen+ SO42- B B OH- OH- 1 O2- in c & 3 O2- in ~ a O2- in ~ bC in c or a SO42- b 0.5 Cl- CO32- OH- OH- OH- B B B c c c Fen+ Fen+ Fen+ A A 0 A OH- OH- OH- From the relative abundances of the doublets D1, D2 and D3 in the Mössbauer spectra, a long range order of Fe cations is deduced as due to an order of anions in interlayers. The models are described in the next figure. ForGR1(CO32-): a = 0.317588(2) nm and c = 2.27123(3) nm

  4. Cl- FeII FeIII (a) CO32- FeII FeIII (b) SO42- FeII FeIII (c) Projections perpendicular to the c axis of the structure of one interlayer, one layer, one interlayer and 3 adjacent interlayers to visualize a repeat for (a) GR1(Cl-), (b) GR1(CO32-)and (c) GR2(SO42-).

  5. The in situ oxidation of the green rust was discovered by pouring H2O2 onto a GR sample, which became orange. In the example of GR1(CO32-), [FeII4FeIII2(OH)12]2+[CO32-3H2O]2-, by injecting progressively with a peristaltic pump H2O2 , one monitored the oxidation by Mössbauer spectra and observed that the two ferrous doublets D1 and D2 transformed progressively into one new ferric doublet D4 up to completion when it became the fully ferric oxyhydroxycarbonate GR*, FeIII6O12H8CO3. Meanwhile, the morphology of the hexagonal crystals did not change (TEM) and diffraction lines of the XRD patterns testified that the structure was essentially conserved. The oxidation process is due to a deprotonation of OH- ions at the apices of the octahedrons surrounding the Fe cations that leads to FeII6(1-x) FeIII6x O12 H2(7-3x) CO3. H2O2 x = 0.50 GR(CO32-) x= 0.33 (b) (a) 003 Intensity (a. u) Intensity (a. u) Intensity (a. u) (b) (a) (c) Diffraction Angle (2q°) Diffraction Angle (2q°) Diffraction Angle (2q°) 0.2 µm 0.2 µm 012 113 006 018 H2O2 x = 1 015 110 (c) 10 10 20 20 30 30 40 40 0.5 µm 10 20 30 40

  6. D2 x = 0.33 Transmittance % x ~ 0.50 D3 Transmittance % D1 H2O2 with H2O2 (b) e 78 K Eh(V) (a) 78 K 0.3 d 0.2 c Velocity (mm s-1) 0.1 D150 % b 0.0 D333 % x = 0.33 Probability density (p) D217 % -0.1 D138 % a D333 % (a) (b) -0.2 100 78 K Probability density (p) D416.5 % x ~ 0.50 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -1 0 1 2 3 D212.5 % Quadrupole splitting D (mm s-1) 78 K {2 × [n(H2O2) / n(Fetotal)] + (1/3)} 99 -1 0 1 2 3 Quadrupole splitting D (mm s-1) x ~ 0.78 Transmittance % x = 1 x ~ 0.63 Transmittance % 98 Transmittance % (e) (d) (c) 78 K 78 K 97 78 K -4 -2 0 2 4 Velocity (mm s-1) D443 % 96 D467 % x ~ 0.78 (d) D431 % D128 % x ~ 0.63 D335 % (e) D1 + D222 % x = 1 Probability density (p) Probability density (p) D333 % D332 % Probability density (p) (c) 95 D29 % 78 K 78 K 78 K 94 -1 0 1 2 3 -1 0 1 2 3 -1 0 1 2 3 -4 -3 -2 -1 0 1 2 3 4 Quadrupole splitting D (mm s-1) Quadrupole splitting D (mm s-1) Quadrupole splitting D (mm s-1) 100 96 -4 -4 -4 -3 -3 -3 -2 -2 -2 -1 -1 -1 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 92 88 84 Velocity (mm s-1) 100 96 92 100 88 98 84 96 Velocity (mm s-1) 100 94 96 92 88 84 Velocity (mm s-1) The in situ oxidation of green rusts by deprotonationUse a strong oxidant such as H2O2, Dry the green rust and oxide in the air, Violent air oxidation, Oxide in a basic medium… FeII6(1-x) FeIII6x O12 H2(7-3x) CO3 FeII-III oxyhydroxycarbonate 0 < x < 1 “Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

  7. The magnetic properties of ferric oxyhydroxycarbonate GR* and FeII-III hydroxycarbonate GR are quite different. GR* is ferromagnetic with ordering around 70 K whereas GR at x = 1/3 is ferrimagnetic with ordering at 5.2 and 7 K for the FeII and FeIII sublattices, respectively. Table of the spectra of the next slide: Mössbauer parameters of stoichiometric FeII-III hydroxycarbonate FeII4FeIII2 (OH)12CO3 measured at low temperatures to determine the magnetic ordering. Temp. (K) Components d (mm s-1) D or e (mm s-1) H (kOe) qb (°) hgb (°) G/2 (mm s-1) 1.4 FeII octet (61%) 1.28 2.91 130 ~87 0.1 ~30 0.20-0.38 FeIII sextet (39%) 0.49 0.2 ~545a 0.18 3.5 FeII octet (51%) 1.31 -2.95 121 ~87 0.15 0.3-0.4 FeII doublet (9%) 1.31 -2.95 0.25 FeIII sextet (38%) 0.46 -0.21 ~510a 0.18 FeIII doublet (2%) 0.46 0.45 0.25 4.2 FeII octet (44%) 1.31 -3.00 110 ~84 0.2 ~95 0.3 FeII doublet (17%) 1.31 -3.00 0.25 FeIII sextet (35%) 0.46 -0.3 ~500a FeIII doublet (4%) 0.46 0.45 0.25 5.5 FeII octet (28%) 1.28 2.92 100 0.3-0.4 FeII doublet (34%) 1.28 2.92 0.25 FeIII sextet (29%) 0.46 0.2 ~500a 0.18 FeIII doublet (9%) 0.46 0.45 0.25 12 FeII doublet (64%) 1.28 -2.86 0.19 FeIII doublet (36%) 0.49 0.42 0.17 12c FeII doublet (49%) 1.29 -2.91 0.17 FeII doublet (19%) 1.29 -2.57 0.17 FeIII doublet (32%) 0.50 0.40 0.17 d: isomer shift with respect to metallic Fe measured at room temperature; D: quadrupole splitting in paramagnetic state or e: quadrupole shift; H: hyperfine magnetic field; q: angle between the electric field gradient (EFG) axis of symmetry with hyperfine field H; h: asymmetry parameter and g: angle between one principle axis of EFG and H ; G/2: half line width at half maximum. a Hyperfine field distribution maximum value.b Approximately computed value.c Better resolution in 4 mms-1 velocity range from Ref. [10]. 100 80 60 Doublet fraction (%) FeII doublet FeIII doublet 40 20 0 5 7 9 10 11 12 0 1 2 3 4 5 6 8 13 Temperature (K) Temperature variations of the proportions of quadrupole doublets for FeII and FeIII components within the Mössbauer spectra of GR(CO32-) 1st 2nd 3rd When x increases from 0 to 1, three cation sublattices are progressively filled with FeIII ions replacing FeII. For each x value, a FeIII cation is surrounded by the minimal number of other FeIII because of repulsion. This is obtained by long range order of periodicity a = a03. sublattice B. Rusch, J.-M. R. Génin, C. Ruby, M. Abdelmoula and P. Bonville, Ferrimagnetic properties in FeII-III (oxy)hydroxycarbonate green rusts, Solid State Sci. 10 (2008) 40-49.

  8. 0.014 100 0.012 100 S1 0.010 S3 0.008 51% 99 Probabability density (au) 34% 0.006 S2 0.004 (a) (b) 15% 95 98 16 K 16 K 0.002 100 0.000 200 300 400 500 600 -10 -5 0 5 10 Hyperfine Magnetic Field H (kOe) Velocity (mm s-1) (b) 3.5 K 100 100 99 95 99 98 100 97 98 (c) 4.2K 96 (c) (d) 60 K 50 K 97 95 Transmission (%) 94 95 -10 -5 0 5 10 -2 -1 0 1 2 Velocity (mm s-1) Velocity (mm s-1) 100 1.0 100 (d) 5.5 K 0.8 D1 98 x = 0.33 67% 0.6 95 Probabilitydensity (au) D3 96 0.4 33% (e) (f) 100 78 K 0.2 94 78 K (e) 12 K 0.0 -1 0 1 2 3 95 -2 -1 0 1 2 Quadrupole Splitting D (mm s-1) Velocity (mm s-1) -10 -5 0 5 10 Velocity (mm s-1) FeII4 FeIII2 (OH)12 CO3 ferrimagnetism FeIII6 O12 H8 CO3 ferromagnetism (a) 1.4 K H = 130 kOe D = -3 mm s-1 • Evolution of Mössbauer spectra with measurement temperature displaying the ferrimagnetic behaviour of stoichiometric GR(CO32-) between 1.4 and 12 K. Mössbauer spectra of GR(CO32-) sample oxidised violently by H2O2 and named ferric [GR(CO32-)*]1. Measurement temperatures are (a) 16 K, (c) 50 K, (d) 60 K and (e) 78 K. (b) and (f) are the hyperfine field distribution of (a) and quadrupole splitting distribution of (e) using a Voigt profile analysis, respectively. “Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

  9. FeII-III oxyhydroxycarbonate Upper Lower layer layer H2O OH- O2- (a) x = 0 (b) x = 0.33 1st sublattice FeII FeII(CO32-) FeII(H2O) 1st sublattice FeIII 2nd sublattice 3rd sublattice { { FeII6(1-x) FeIII6x O12 H2(7-3x) CO3 (d) x = 1 (c) x = 0.67 Projections perpendicular to the c axis of a Fe layer with octahedrons of OH- ions that can be deprotonated or protonated for values of x = 0, 0.33, 0.67 and 1. There exist four ordered types of domain to match any intermediate composition as determined by x.

  10. x = 0 x = 0.33 0.33 < x < 0.67 Ferri b (c) H FeIII FeII 0.67 < x < 1 x = 1 x = 0.67 Ferro Ferri (e) FeIII (f) (d) FeIII FeII FeIII FeII a (a) (b) FeII FeIII FeII Hexagonal pavements of FeII and FeIII cations in the layers of (a) Fe(OH)2, (b) stoichiometric GR(CO32-) at x = 1/3, (c) GR(CO32-)* with 1/3 < x < 2/3, (d) GR(CO32-)* at x = 2/3, (e) GR(CO32-)* with 2/3 < x < 1 and (f) fully ferric GR(CO32-)* at x = 1. Long range order is displayed showing magnetic domains.

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