• Images
• Videos
• Documents
• Books
• Articles

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.²³ The β form adopts a hexagonal close-packed structure of Ni2+ and OH− ions.⁴⁵ In the presence of water, the α polymorph typically recrystallizes to the β form.⁶⁷ 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.⁸

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.⁹ A nickel-magnesium variant of the mineral, (Ni,Mg)(OH)2 had been previously discovered at Hagdale on the island of Unst in Scotland.¹⁰

Reactions

Nickel(II) hydroxide is frequently used in electrical car batteries.¹¹ 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).¹²¹³

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.¹⁴

Synthesis

The synthesis entails treating aqueous solutions of nickel(II) salts with potassium hydroxide. When the same reaction is conducted in the presence of bromine, the product is Ni3O2(OH)4.¹⁵

Toxicity

The Ni2+ ion is a carcinogen when inhaled.

See also

• List of minerals named after people
• Nickel–cadmium battery
• Nickel–hydrogen battery
• Nickel–metal hydride battery
• Nickel–iron battery

References

1. Chen, J.; Bradhurst, D.H.; Dou, S.X.; Liu, H.K. (1999). "Nickel Hydroxide as an Active Material for the Positive Electrode in Rechargeable Alkaline Batteries". Journal of the Electrochemical Society. 146 (10): 3606–3612. Bibcode:1999JElS..146.3606C. doi:10.1149/1.1392522. S2CID 33058220. https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1118&context=engpapers ↩

2. Oliva, P.; Leonardi, J.; Laurent, J.F. (1982). "Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides". Journal of Power Sources. 8 (2): 229–255. Bibcode:1982JPS.....8..229O. doi:10.1016/0378-7753(82)80057-8. /wiki/Bibcode_(identifier) ↩

3. Jeevanandam, P.; Koltypin, Y.; Gedanken, A. (2001). "Synthesis of Nanosized α-Nickel Hydroxide by a Sonochemical Method". Nano Letters. 1 (5): 263–266. Bibcode:2001NanoL...1..263J. doi:10.1021/nl010003p. /wiki/Bibcode_(identifier) ↩

4. Oliva, P.; Leonardi, J.; Laurent, J.F. (1982). "Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides". Journal of Power Sources. 8 (2): 229–255. Bibcode:1982JPS.....8..229O. doi:10.1016/0378-7753(82)80057-8. /wiki/Bibcode_(identifier) ↩

5. Jeevanandam, P.; Koltypin, Y.; Gedanken, A. (2001). "Synthesis of Nanosized α-Nickel Hydroxide by a Sonochemical Method". Nano Letters. 1 (5): 263–266. Bibcode:2001NanoL...1..263J. doi:10.1021/nl010003p. /wiki/Bibcode_(identifier) ↩

6. Oliva, P.; Leonardi, J.; Laurent, J.F. (1982). "Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides". Journal of Power Sources. 8 (2): 229–255. Bibcode:1982JPS.....8..229O. doi:10.1016/0378-7753(82)80057-8. /wiki/Bibcode_(identifier) ↩

7. Shukla, A.K.; Kumar, V.G.; Munichandriah, N. (1994). "Stabilized α-Ni(OH)2 as Electrode Material for Alkaline Secondary Cells". Journal of the Electrochemical Society. 141 (11): 2956–2959. Bibcode:1994JElS..141.2956V. doi:10.1149/1.2059264. /wiki/Bibcode_(identifier) ↩

8. Oliva, P.; Leonardi, J.; Laurent, J.F. (1982). "Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides". Journal of Power Sources. 8 (2): 229–255. Bibcode:1982JPS.....8..229O. doi:10.1016/0378-7753(82)80057-8. /wiki/Bibcode_(identifier) ↩

9. Marcopoulos, T.; Economou, M. (1980). "Theophrastite, Ni(OH)2, a new mineral from northern Greece" (PDF). American Mineralogist. 66: 1020–1021. http://www.minsocam.org/ammin/AM66/AM66_1020.pdf ↩

10. Livingston, A.; Bish, D. L. (1982). "On the new mineral theophrastite, a nickel hydroxide, from Unst, Shetland, Scotland" (PDF). Mineralogical Magazine. 46 (338): 1. Bibcode:1982MinM...46....1L. doi:10.1180/minmag.1982.046.338.01. S2CID 8381523. http://www.minersoc.org/pages/Archive-MM/Volume_46/46-338-1.pdf ↩

11. Jeevanandam, P.; Koltypin, Y.; Gedanken, A. (2001). "Synthesis of Nanosized α-Nickel Hydroxide by a Sonochemical Method". Nano Letters. 1 (5): 263–266. Bibcode:2001NanoL...1..263J. doi:10.1021/nl010003p. /wiki/Bibcode_(identifier) ↩

12. Ovshinsky, S.R.; Fetcenko, M.A.; Ross, J. (1993). "A nickel metal hydride battery for electric vehicles". Science. 260 (5105): 176–181. Bibcode:1993Sci...260..176O. doi:10.1126/science.260.5105.176. PMID 17807176. S2CID 9523468. /wiki/Bibcode_(identifier) ↩

13. Young, Kwo (2016). Nickel Metal Hydride Batteries. MDPI. doi:10.3390/books978-3-03842-303-4. ISBN 978-3-03842-303-4. 978-3-03842-303-4 ↩

14. Shukla, A.K.; Kumar, V.G.; Munichandriah, N. (1994). "Stabilized α-Ni(OH)2 as Electrode Material for Alkaline Secondary Cells". Journal of the Electrochemical Society. 141 (11): 2956–2959. Bibcode:1994JElS..141.2956V. doi:10.1149/1.2059264. /wiki/Bibcode_(identifier) ↩

15. O. Glemser (1963). "Nickel (II) Hydroxide and Nickel (II,III) Hydroxide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. New York: Academic Press. p. 1549-1551. ↩