Nickel (II) Chloride

Nickel (II) chloride (NiCl₂) or Nickel Dichloride is a water-soluble crystalline solid.  As a hexahydrate it has a green color while the anhydrous form is yellow.  Both forms are deliquescent and must be protected from moisture in storage.  Nickel (II) Chloride has applications in many industries, including electroplating, dyes and pigments, catalyst production, and the synthesis of Nickel-containing materials.

Aqueous solutions of both Nickel Chloride and Nickel Sulfate are commonly used in solutions for electroplating nickel, since they are both highly soluble.  Solutions made with Nickel Chloride are more corrosive than those made with Nickel Sulfate.  However, the solutions are more conductive, reducing power consumption during the deposition process.  In addition, the Nickel coating is more uniform.  In practice, deposition solutions may contain a mixture of both nickel salts.

Nickel ions are also redox-active and can be used to prepare catalysts.  For example, chemists from the chemical company Rhône-Poulenc in Paris were searching for a replacement for Raney Nickel catalyst, which is pyrophoric.  They were able to prepare Nickel Boride catalysts by reacting Nickel Chloride hexahydrate with Sodium Borohydride.  The catalyst was effective at hydrogenation and easier to store and handle.  Across the globe at Kyoto University in Japan, chemical engineers prepare a different catalyst for hydrogenation, using anhydrous Nickel Chloride and methylhydropolysiloxane.

Nickel dichloride can also be used to prepare Nickel-Oxide-based materials.  The decomposition of Nickel Chloride hydrate to Nickel Oxide is complex, but the material is completely converted to nickel oxide above 850 degrees Celsius. However, thin films of nickel oxide can be prepared at lower temperatures.  Researchers at Alagappa University in Karaikudi, India produced Nickel Oxide thin films by spraying aqueous Nickel (II) Chloride onto heated glass, where it is rapidly deposited via evaporation and pyrolytic decomposition. These films are electrochromic and useful in sensors and solar cells.

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