Nickel(II) hydroxide
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| Names | |
|---|---|
| IUPAC name
Nickel(II) Hydroxide | |
| Other names
Nickel Hydroxide, Theophrasite | |
| Identifiers | |
12054-48-7  36897-37-7 (monohydrate)  | |
| ChemSpider | 55452 |
| EC Number | 235-008-5 |
| Jmol 3D model | Interactive image |
| PubChem | 61534 |
| RTECS number | QR648000 |
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| Properties | |
| Ni(OH)2 | |
| Molar mass | 92.724 g/mol (anhydrous) 110.72 g/mol (monohydrate) |
| Appearance | green crystals |
| Density | 4.10 g/cm3 |
| Melting point | 230 °C (446 °F; 503 K) (anhydrous, decomposes) |
| 0.013 g/100 mL | |
| Solubility | soluble in dilute acid, ammonia (monohydrate) |
| Structure | |
| hexagonal | |
| Thermochemistry | |
| Std molar entropy (S |
79 J·mol−1·K−1[1] |
| Std enthalpy of formation (ΔfH |
−538 kJ·mol−1[1] |
| Hazards | |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose) |
1515 mg/kg (oral, rat) |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| verify (what is ?) | |
| Infobox references | |
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Nickel(II) hydroxide is the inorganic compound with the formula Ni(OH)2. It is an apple-green solid that dissolves with decomposition in ammonia and amines and is attacked by acids. It is electroactive, being converted to the Ni(III) oxy-hydroxide, leading to widespread applications in rechargeable battery.[2]
Properties
Nickel(II) hydroxide has two well-characterized polymorphs, α and β. The α structure consists of Ni(OH)2 layers with intercalated anions or water.[3][4] The β form adopts a hexagonal close-packed structure of Ni2+ and OH− ions.[3][4] In the presence of water, the α polymorph typically recrystallizes to the β form.[3][5] In addition to the α and β polymorphs, several γ nickel hydroxides have been described, distinguished by crystal structures with much larger inter-sheet distances.[3]
The mineral form of Ni(OH)2, theophrastite, was first identified in the Vermion region of northern Greece, in 1980. It is found naturally as a translucent emerald-green crystal formed in thin sheets near the boundaries of idocrase or chlorite crystals.[6] A nickel-magnesium variant of the mineral, (Ni,Mg)(OH)2 had been previously discovered at Hagdale on the island of Unst in Scotland.[7]
Reactions
Nickel (II) hydroxideis frequently used in electrical car batteries.[4] Specifically, Ni(OH)2 readily oxidizes to nickel oxyhydroxide, NiOOH, in combination with a reduction reaction, often of a metal hydride (reaction 1 and 2).[8]
Reaction 1 Ni(OH)2 + OH− → NiO(OH) + H2O + e−
Reaction 2 M + H2O + e− → MH + OH−
Net Reaction (in H2O) Ni(OH)2 + M → NiOOH + MH
Of the two polymorphs, α-Ni(OH)2 has a higher theoretical capacity and thus is generally considered to be preferable in electrochemical applications. However, it transforms to β-Ni(OH)2 in alkaline solutions, leading to many investigations into the possibility of stabilized α-Ni(OH)2 electrodes for industrial applications.[5]
Synthesis
The synthesis entails treating aqueous solutions of nickel(II) salts with potassium hydroxide.[9]
Toxicity
The Ni2+ ion is a known carcinogen. Toxicity and related safety concerns have driven research into increasing the energy density of Ni(OH)2 electrodes, such as the addition of calcium or cobalt hydroxides.[2]
See also
References
- 1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
- 1 2 Chen, J.; Bradhurst, D.H.; Dou, S.X.; Liu, H.K. J. Electrochem. Soc. 1999. 146, 3606-3612.
- 1 2 3 4 Oliva, P.; Leonardi, J.; Laurent, J.F. Journal of Power Sources. 1982, volume 8, 229-255.
- 1 2 3 Jeevanandam, P.; Koltypin, Y.; Gedanken, A. Am. Chem. Soc. Nano Letters. 2001, 1, 263-266.
- 1 2 Shukla, A.K.; Kumar, V.G.; Munichandriah, N. J. Electrochem. Soc.1994, 141, 2956-2959.
- ↑ Marcopoulos, T.; Economou, M. American Mineralogist, 1980, 66, 1020-1021.
- ↑ Livingston, A. and Bish, D. L. (March 1982) "On the new mineral theophrastite, a nickel hydroxide, from Unst, Shetland, Scotland". Mineralogical Magazine. 6 No. 338.
- ↑ Ovshinsky, S.R.; Fetcenko, M.A.; Ross, J. Science. 1993, 260, 176-181.
- ↑ O. Glemser "Nickel(II) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1549.
External links
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