Nickel(II) hydroxide

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Nickel(II) hydroxide
Nickel(II) hydroxide
Nickel(II) hydroxide
Names
IUPAC name
Nickel(II) Hydroxide
Other names
Nickel Hydroxide, Theophrasite
Identifiers
12054-48-7 YesY
36897-37-7 (monohydrate) N
ChemSpider 55452 YesY
EC Number 235-008-5
Jmol 3D model Interactive image
PubChem 61534
RTECS number QR648000
  • InChI=1S/Ni.2H2O/h;2*1H2/q+2;;/p-2 YesY
    Key: BFDHFSHZJLFAMC-UHFFFAOYSA-L YesY
  • InChI=1/Ni.2H2O/h;2*1H2/q+2;;/p-2
    Key: BFDHFSHZJLFAMC-NUQVWONBAJ
  • [Ni+2].[OH-].[OH-]
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
79 J·mol−1·K−1[1]
−538 kJ·mol−1[1]
Vapor pressure {{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references
File:DSC01973 - Nickel (II) reactions.JPG
The test tube in the middle contains a precipitate of nickel(II) hydroxide

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. ↑ 1.0 1.1 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 Chen, J.; Bradhurst, D.H.; Dou, S.X.; Liu, H.K. J. Electrochem. Soc. 1999. 146, 3606-3612.
  3. ↑ 3.0 3.1 3.2 3.3 Oliva, P.; Leonardi, J.; Laurent, J.F. Journal of Power Sources. 1982, volume 8, 229-255.
  4. ↑ 4.0 4.1 4.2 Jeevanandam, P.; Koltypin, Y.; Gedanken, A. Am. Chem. Soc. Nano Letters. 2001, 1, 263-266.
  5. ↑ 5.0 5.1 Shukla, A.K.; Kumar, V.G.; Munichandriah, N. J. Electrochem. Soc.1994, 141, 2956-2959.
  6. ↑ Marcopoulos, T.; Economou, M. American Mineralogist, 1980, 66, 1020-1021.
  7. ↑ 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.
  8. ↑ Ovshinsky, S.R.; Fetcenko, M.A.; Ross, J. Science. 1993, 260, 176-181.
  9. ↑ 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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