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FeCl2 is trigonal omega-like structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three FeCl2 sheets oriented in the (0, 0, 1) direction. Fe2+ is bonded to six equivalent Cl1- atoms to form edge-sharing FeCl6 octahedra. All Fe–Cl bond lengths are 2.47 Å. Cl1- is bonded in a distorted T-shaped geometry to three equivalent Fe2+ atoms.
Here, we report for the first time the formation of a HP-PdF 2 -type FeCl 2 phase (space group Pa$\bar{3}$), through high pressure-temperature (P-T) reactions in the hydrous systems (Mg 0.6 Fe 0.4 )SiO 3 –H 2 O–NaCl and FeO2H–NaCl in a laser-heated diamond-anvil cell up to 108 GPa and 2000 K. Applying single-crystal X-ray diffraction (XRD) analysis to individual submicrometer-sized grains, we have successfully determined the crystal structure of the as-synthesized FeCl 2 phase, in agreement with our theoretical structure search results. In situ high P-T XRD data revealed the substitution of Cl for OH(O) in such a cubic Pa$\bar{3}$ structure, demonstrating that this topology is a potential host for both H and Cl in the deep Earth. The chemical analysis of the recovered sample showed that the post-perovskite phase contains considerable amounts of Na 2 O and Fe 2 O 3 . The coexistence of the cubic FeCl 2 phase and post-perovskite suggests that the lowermost mantle could be a potential reservoir of Cl. The possible presence of volatiles such as H and Cl in the deep lower mantle would impact the composition and iron valence state of the post-perovskite phase.
FeCl2(O)4Sb(OCl3)2O2 crystallizes in the triclinic P1 space group. The structure is one-dimensional and consists of one hydrogen peroxide molecule; one FeCl2(O)4 cluster; and one Sb(OCl3)2 ribbon oriented in the (1, 0, 0) direction. In the FeCl2(O)4 cluster, Fe is bonded in a 6-coordinate geometry to four O and two Cl atoms. There are a spread of Fe–O bond distances ranging from 1.83–2.14 Å. There are one shorter (2.28 Å) and one longer (2.29 Å) Fe–Cl bond lengths. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Fe atom. In the second O site, O is bonded in a 2-coordinate geometry to one Fe and one O atom. The O–O bond length is 1.28 Å. In the third O site, O is bonded in a single-bond geometry to one Fe atom. In the fourth O site, O is bonded in a 2-coordinate geometry to one Fe and one O atom. There are two inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Fe atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Fe atom. In the Sb(OCl3)2 ribbon, Sb is bonded in an octahedral geometry to six Cl atoms. There are a spread of Sb–Cl bond distances ranging from 2.36–2.51 Å. There are two inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to one O and two Cl atoms. The O–O bond length is 2.01 Å. There are one shorter (2.41 Å) and one longer (2.50 Å) O–Cl bond lengths. In the second O site, O is bonded in a distorted L-shaped geometry to one O and one Cl atom. The O–Cl bond length is 2.45 Å. There are six inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Sb atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Sb atom. In the third Cl site, Cl is bonded in a single-bond geometry to one Sb and one O atom. In the fourth Cl site, Cl is bonded in a single-bond geometry to one Sb and one O atom. In the fifth Cl site, Cl is bonded in a single-bond geometry to one Sb atom. In the sixth Cl site, Cl is bonded in a distorted single-bond geometry to one Sb and one O atom.
Transitioning from fossil-fuels to renewable energy sources is a critical goal of greenhouse gas re-duction and climate control. Major improvements have made wind and solar power increasingly cost-competitive with fossil fuels. However, the inherent intermittency of renewable power sources such motivates pairing these resources with energy storage. Electrochemical energy storage in batteries is widely used in many fields and increasingly for grid-level storage, but current battery technologies still fall short of performance, safety, and cost. This review focuses on sodium metal halide (Na-MH) batteries, such as well-known Na-NiCl2 batteries, as a promising solution to safe and economical grid-level energy storage. Important features of conventional Na-MH batteries are discussed, and recent literature on the development of intermediate temperature, low-cost cathodes for Na-MH batteries is highlighted. By employing lower cost metal halides (e.g. FeCl2, ZnCl2, and CuCl2, etc.) in the cathode and operating at lower temperatures (e.g. 190 °C vs. 280 °C), new Na-MH batteries have the potential to offer comparable performance at much lower overall costs, providing an exciting alternative technology to enable widespread adoption of renewables plus storage for the grid.
Experiments were conducted to determine the nature of the alteration process in lunar rocks. Mixtures of 10 wt.% Fe + 10 wt.% FeCl2 + 80 wt.% basalt (terrestrial) were pelletized and allowed to set for 48 hrs at 25 C, at 40% and at 100% relative humidity. The end products were examined by reflected-light microscopy and by X-ray diffraction. The degree of reaction appears to depend upon the amount of FeCl2, the availability of water and the Ni content of the metallic Fe. The experiments showed the extremely rapid rate at which the oxyhydration can occur in air and that the product is beta-FeOOH. The data from the FeOOH mineral in rock 66095 were compared with those obtained from synthetic beta-FeOOH and found to be identical. The 'rust' in the Apollo 16 rocks could result from oxyhydration of the samples, caused by water vapor contamination, all or part of which occurred in the Apollo spacecraft and/or upon return to earth. The akageneite (beta-FeOOH) in lunar rocks could be entirely of terrestrial origin as originally suggested by Taylor et al. (1973).
The reaction of iron with 1 percent HCl/0-50 percent O2/Ar has been studied at 550 C with thermogravimetry to monitor kinetics and scanning electron microscopy to characterize product morphologies. In addition, the volatile species were identified with an atmospheric pressure sampling mass spectrometer. The reaction of 1 percent HCl/Ar produces FeCl2. The reactions of 1 percent HCl/1, 10, 50 percent O2/Ar produce Fe2O3, Fe3O4, FeCl2, and FeCl3. In each case condensed phase chlorides form at the oxide/metal interface where the oxygen potential is low. The 10 and 50 percent oxygen mixtures have kinetics in the first 3 hr similar to pure oxidation with some deviations due to iron-chloride formation. The 1 percent oxygen mixture shows enhanced reaction rates over oxidation, very likely due to the formation of a porous scale.
Preliminary fundamental investigations aimed at evaluating sodium metal chloride systems for future aerospace applications are described. Since the sodium metal chloride systems are relatively new, the approach has been to characterize their fundamental properties in order to understand their limitations. To this end, a series of fundamental electrochemical investigations have been carried out, the results of which are reported here. The metal chloride cathodes show high exchange current densities which corroborate their good reversibility in a battery application. The reduction mechanisms appear to be complex and involve multielectron transfer steps and intermediates. Such intermediates in the reaction mechanism have already been identified in the case of FeCl2. Similar mechanisms may be operative in the case of NiCl2. CuCl2, however, exhibits a second relaxation loop in the impedance plot at low frequencies and also a sloping discharge curve, unlike FeCl2 and NiCl2, which may indicate the existence of monovalent copper in the reduction mechanism.
Carbon materials containing iron alloy, iron metal, iron oxide or iron halide were fabricated. Typical samples of these metals were estimated to contain 1 iron atom per 3.5 to 5 carbon atoms. Those carbon materials containing iron alloy, iron metal, and/or Fe3O4 were magnetic. The kinetics of the fabrication process were studied by exposing graphite fluoride (CF(0.68)) to FeCl3 over a 280 to 420 C temperature range. Between 280 and 295 C, FeCl3 quickly entered the structure of CF(0.68), broke the carbon-fluorine bonds, and within 10 to 30 min, completely converted it to carbon made up of graphite planes between which particles of crystalline FeF3 and noncrystalline FeCl3 were located. Longer reaction times (e.g., 28 hr) or higher reaction temperatures (e.g., 420 C) produced materials containing graphite, a FeCl3-graphite intercalation compound, FeCl2(center dot)4H2O, and FeCl2(center dot)2H2O. These products were further heat treated to produce iron-containing carbon materials. When the heating temperature was kept in the 750 to 850 C range, and the oxygen supply was kept at the optimum level, the iron halides in the carbon structure were converted to iron oxides. Raising the heat to temperatures higher than 900 C reduced such iron oxides to iron metal. The kinetics of these reactions were used to suggest processes for fabricating carbon materials containing iron alloy. Such processes were then tested experimentally. In one of the successful trial runs, commercially purchased CF(0.7) powder was used as the reactant, and NiO was added during the final heating to 1200 C as a source of both nickel and oxygen. The product thus obtained was magnetic and was confirmed to be a nickel-iron alloy in carbon.
Following the disclosures by Coetzer et al. on the use of transition metal chlorides in chloroaluminates as alternate cathodes to sulfur in rechargeable sodium batteries, several laboratories, including the Jet Propulsion Laboratory, focused their attention on these systems. These systems have certain distinct advantages over sodium-sulfur batteries such as increased safety, inherent overcharge capability, and lower operating temperatures. Two systems, i.e., Na/FeCl2 and NaNiCl2, were developed extensively and evaluated in various applications including electric vehicles and space. Their performance has been very encouraging and warrants a detailed fundamental study on these cathodes. At the Jet Propulsion Laboratory a program was initiated two years back to understand the electrochemical behavior of FeCl2 and NiCl2, and to identify and evaluate other transition metal chlorides of promise. The initial efforts focused on the methods of fabrication of the electrodes and their electrochemical characterization. Subsequent studies were aimed at establishing the reaction mechanism, determining the kinetics, and identifying the rate-limiting processes in te reduction of metal chloride cathodes. Nickel chloride emerged form these studies as the most promising candidate material and was taken up for further detailed study on its passivation- a rate limiting process-under different experimental conditions. Also, the feasibility of using copper chloride, which is expected to have a higher energy density, has been assessed. On the basis of the criteria established from the voltammetric response of FeCl2, NiCl2, and CuCl2, several other transition metal chlorides were screened. Of these, molybdenum and cobalt appear promising.
FeCl2(H2O)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Fe2+ is bonded in a distorted octahedral geometry to four O2- and two equivalent Cl1- atoms. There are two shorter (2.12 Å) and two longer (2.21 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.53 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Cl1- atom. The H–O bond length is 1.00 Å. The H–Cl bond length is 2.10 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Cl1- atom. The H–O bond length is 0.99 Å. The H–Cl bond length is 2.14 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Fe2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Fe2+ and two H1+ atoms. Cl1- is bonded in a 1-coordinate geometry to one Fe2+ and two H1+ atoms.
FeCl2(H2O)4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two 13478-10-9 molecules. Fe2+ is bonded in an octahedral geometry to four O2- and two equivalent Cl1- atoms. There are two shorter (2.11 Å) and two longer (2.13 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.55 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Fe2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Fe2+ and two H1+ atoms. Cl1- is bonded in a single-bond geometry to one Fe2+ atom.
FeCl2(O)4SbCl6(O2)2 crystallizes in the tetragonal P4/mmm space group. The structure is zero-dimensional and consists of one dichloroiron;tetrahydrate molecule, four water molecules, and one SbCl6 cluster. In the SbCl6 cluster, Sb is bonded in an octahedral geometry to six Cl atoms. There are two shorter (2.36 Å) and four longer (2.44 Å) Sb–Cl bond lengths. There are two inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Sb atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Sb atom.
FeCl2(O)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Fe is bonded in a distorted square co-planar geometry to four O and two equivalent Cl atoms. There are two shorter (2.03 Å) and two longer (2.09 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.88 Å. There are two inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Fe and one Cl atom. The O–Cl bond length is 1.58 Å. In the second O site, O is bonded in a bent 120 degrees geometry to one Fe and one Cl atom. The O–Cl bond length is 1.58 Å. Cl is bonded in a distorted trigonal non-coplanar geometry to one Fe and two O atoms.
Apollo 16 samples of all four rock types and from all stations contain evidence for hydration and oxidation - i.e., the presence of hydrated iron oxide, probably goethite. Rock 66095 contains native FeNi grains with a characteristic intergrowth of schreibersite and, to lesser extents, of cohenite. Troilite also contains sphalerite. The goethite contains 1.5-4.6 wt.% chlorine and occurs mainly on the edges of FeNi metal, causing a rust color in the cracks and space around the native metal grains, which also contain abundant chlorine. This observation suggests the presence of lawrencite (FeCl2), a phase that deliquesces and oxidizes very rapidly upon exposure to water or to a moist atmosphere.
Potentiostatic determinations in various mixtures of FeCl2-FeCl3 with excess HCl show rest potentials that are 0.1 V less electropositive than the theoretical values from the formulated ratios of FeII to FeIII (probably as a result of complexing). The standard rate constant sub s. ranges between 0.0001 and 0.000 cm/sec. Tafel slopes b of roughly 0.12V per decade indicate single-electron exchange kinetics. No significant trend in either b or sub s was attributed to mixture composition. The higher sub s. values occurred with and edge-on pyrolytic graphite that had undergone a permanent surface change.
In a study of biochemical means of solar energy conversion, ADP and inorganic phosphates were converted to ATP by white light in the nonaqueous solvent dimethylformamide in the presence of tetrachloro-p-quinone or ubiquinone. Conversion of ADP to ATP has been accomplished in aqueous suspension by the use of cell-like structures aggregated from poly(aspartic acid, glutamic acid, tyrosine). This is believed to occur through the formation of dopaquinone in the peptide structure during illumination. The way in which the quantitative yield of ATP has been influenced by pH and by added substances, such as FeCl2, was studied.
Thermal release profiles of Pb, Zn, and Cd in sample 66095 (highly shocked breccia with melt rock matrix) showed that these volatiles were mostly present on the surface of the grains. Zn in rusty grains from 66095 was also mostly surface Zn, probably from sphalerite in grain boundaries and cracks. Simulation experiments of volatile transfer showed that Fe, FeCl2, iron phosphide, and troilite (FeS) can be produced and transported during subsolidus reactions. These results suggest that volatiles, rust, schreibersite, and possible siderophiles which are observed in lunar highland samples might have been redistributed during disequilibrium thermal metamorphism in hot ejecta blankets, and were not necessarily introduced by volcanic activity or meteoritic addition.
The chromium and iron chloride chemicals are significant first costs for NASA Redox energy storage systems. This study was performed to determine the lowest cost at which chromium and iron chlorides could be obtained for a complex of redox energy storage systems. In addition, since the solutions gradually become intermixed during the course of operation of Redox units, it was an objective to evaluate schemes for regeneration of the operating solutions. Three processes were evaluated for the production of chromium and iron chlorides. As a basis for the preliminary plant design and economic evaluation, it was assumed that the plant would produce about 25,000 tons of contained chromium as CrCl3 and an equivalent molar quantity of FeCl2. Preliminary plant designs, including materials and energy balances and sizing of major equipment, were prepared, and capital and operating costs were estimated.