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Electrochemistry

Electrochemistry
Precious Metal Compounds for the Manufacture of Electrodes and Batteries
Electrochemical processes are chemical methods using electric current. Today they are utilised in the chemical and plating industries (electronics and jewelry ) for large-scale syntheses, and also for advanced power technologies, as well as for ordinary sources of current.
When consuming energy to enforce a reaction, electrochemical processes need an external power source. This method is called "Electrolysis".
However, when a chemical reaction runs spontaneously in the opposite direction by generating electric energy, this is the function of a "Battery".

In either case so-called "Electrodes" mediate the current flow through the - mostly liquid - reaction medium. There are anodes for oxidations, and cathodes for reductions.
Due to their corrosion resistance and their electrical properties, the platinum group metals (PGM's); platinum, iridium, ruthenium, and also silver, play a very important part in the manufacture of electrodes on a large scale.
Moreover, Heraeus manufactures dispersed metals (“Blacks”) for coating of electrochemical sensors.
Our Chemical Products Business Unit manufactures suitable compounds and solutions as core products, which serve to coat or to produce such electrodes.
• Electrodes for electrolysis and electroplating
are made of materials resistent to reaction solutions, and therefore themselves do not corrode or undergo dissolution in the electrochemical process.

Apart from electrodes of metallic platinum (foils, plates, etc.), there is use of anodes that are mainly based on expanded metals showing a lattice structure coated with PGM's (e.g. titanium).

Electrodes coated with platinum only, are often used for simple electrolysis systems (e.g. to protect from corrosion; as cathodes for aqueous solutions; in analytical chemistry; and in part for electroplating).

Anodes coated with oxides of iridium and of ruthenium are used for industrial processes in very aggressive media and for strongly oxidating products (e.g. water electrolysis for producing oxygen; or "Chlor-Alkali Electrolysis" for the combined manufacture of chlorine gas and sodium hydroxide solution). These anodes are usually called Dimensionally Stable Anodes (DSA). This coating improves the electrical properties of the anodes, and makes them resistant to passivation and abrasion.

For coating, precious metal compounds are mostly applied in the form of their solutions. They are decomposed pyrolytically, and so the metals are strongly connected with the surface material.

Heraeus` Precious metal chemicals for the coating of anodes are:

• Dihydrogen hexachloroplatinate(IV) hydrate, H2[PtCl6]•nH2O ("CPA")
• Sodium hexahydroxoplatinate(IV), Na2[Pt(OH)6]
• Potassium hexahydroxoplatinate(IV), K2[Pt(OH)6]
• Dihydrogen hexahydroxoplatinate(IV), H2[Pt(OH)6]
• Bis(acetylacetonato)platinum(II), [Pt(acac)2]
• cis-Diamminedinitritoplatinum(II) solution, cis-[Pt(NO2)2(NH3)2]
• Dihydrogen hexachloroiridate(IV) solution, H2[IrCl6] ("CIA")
• Ruthenium(III) chloride hydrate, RuCl3•nH2O
• Iridium(III) chloride hydrate, IrCl3•nH2O
• Iridium(IV) chloride hydrate, IrCl4•nH2O
• Batteries
are electrochemical cells for gaining energy. For special high-yield batteries (for button battery cells, or in the space industry), silver oxides are used for cathodes (reduction to elemental silver).

Heraeus supplies silver chemicals for the manufacture of batteries, e.g.:

• Silver(I) oxide, Ag2O
• Silver(II) oxide, AgO

Fuel cells generate electric power by the direct and controlled chemical conversion of high-energy reactants ("combustion"). For example, industry is striving for the slow reaction of the "fuel" hydrogen (H2) with oxygen (O2) leaving ecologically harmless water (H2O). Therefore, fuel cells are of particular interest to automotive and communication technologies and to hermetically sealed systems (spacecrafts).

For some fuel cells, platinum crystallites and alloys, which are deposited on e.g. carbon modifications, serve as catalytically active electrodes. Other PGM's are being tested, too.

For the production of fuel cells, Heraeus manufactures e.g.:

• Dihydrogen hexachloroplatinate(IV) hydrate, H2[PtCl6]•nH2O ("CPA")
• Platinum black, Pt

Electrochemical sensors – inter alia - serve to detect toxic gasses (e.g. CO). For this application various carriers are coated with precious metals.

For the production of sensors, Heraeus offers e.g.:

• Dihydrogen hexachloroplatinate(IV) hydrate, H2[PtCl6]•nH2O ("CPA")
• Platinum black, Pt
• Dihydrogen hexachloroiridate(IV) solution, H2[IrCl6]
• Iridium black, Ir
• Ruthenium(III) chloride hydrate, RuCl3•nH2O
• Ruthenium black, Ru
The latest methods of generating energy are based on dye-sensitized solar cells (“Solar Dyes”). You can find more information here .
We look forward to your enquiries and are at your disposal at any time. Should you not find the product you are searching for, please feel free to contact us.
Our company also offers you the recovery of precious metals.For this, please, visit the web page of our Recycling business unit.

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