Electrochemical processes are chemical methods using electric current. Today they are utilized in the chemical industries 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: In the electrolysis electrodes mediate the current flow through the - mostly liquid - reaction medium. 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. Heraeus manufactures suitable compounds and solutions as core products, which serve to coat or to produce such electrodes. Moreover, Heraeus produces dispersed metals (“Blacks”) for coating of electrochemical sensors.
Electrodes and Sensor Technology

Anodes coated with oxides of iridium and of ruthenium are used for industrial processes in very aggressive media and for strongly oxidating products like the chlorine-alkaline electrolysis. 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.
Compound | CAS Number | Formula | Metal Cont. approx. | Color | Samples |
---|---|---|---|---|---|
Ruthenium(III) chlorid hydrate | 14898-67-0 |
RuCl3 · n H2O |
40 % | brownish black | |
Ruthenium(III) chloride solution | 14898-67-0 | RuCl3 | up to 20 % | brown | |
Trinitratonitrosylruthenium(II) | 34513-98-9 | [Ru(NO3)3(NO)] | 30 % | reddish brown | Buy online |
Trinitratonitrosylruthenium(II) solution | 34513-98-9 | [Ru(NO3)3(NO)] | up to 15 % | claret | Buy online |
Dihydrogen hexachloroiridate(IV) hydrate | 16941-92-7 | H2[IrCl6] · n H2O | 43 % | black | |
Dihydrogen hexachloroiridate(IV) solution, “Chloroiridic Acid”; “CIA” | 16941-92-7 | H2[IrCl6] | up to 25 % | brown | |
Iridium(III) chloride hydrate | 14996-61-3 | IrCl3 · n H2O | 54 % | black | |
Iridium(III) chloride hydrate, Type G | 14996-61-3 | IrCl3 · n H2O | 54 % | green | |
Iridium(IV) chloride hydrate | 10025-97-5 | IrCl4 · n H2O | 53 % | black | |
Iridium(III) chloride solution | 10025-83-9 | IrCl3 | up to 10 % | dark brown |
Fuel cells generate electric power by the direct and controlled chemical conversion of high-energy reactants. For example, industry is striving for the controlled reaction of the "fuel" hydrogen H2 with oxygen O2 to water H2O. Therefore, fuel cells are of particular interest to automotive and communication technologies and to hermetically sealed systems like 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.
Those Pt-based materials also used in polymer electrolyte membrane (PEM) electrolysis for the generation of H2, the energy source of the future. Moreover, Iridium-based materials are simultaneously applied for the necessary water splitting into O2.
Compound | CAS Number | Formula | Metal Cont. approx. | Color |
---|---|---|---|---|
Dihydrogen hexachloroplatinate(IV) hydrate “Chloroplatinic Acid“, “CPA” | 26023-84-7 | H2[PtCl6] · n H2O | 40 % | orange |
Platinum black | 7440-06-4 | Pt | 90-100 % | black |
Pt nanoparticles on Carbon | 7440-06-4 | Pt/C | 10-40 % | black |
Iridium black | 7439-88-5 | Ir | 98 % | black |
Iridium(IV)oxide | 12030-49-8 | IrO2 | 85-86 % | black |
Iridium-Ruthenium-Oxides | IrxRu1-xO2 (0 < x < 1) | 76-86 % | black | |
Ruthenium(III) chlorid hydrate | 14898-67-0 | RuCl3 · n H2O | 40 % | brownish black |
Platinum oxalate | blue |
Electrochemical sensors serve to detect toxic gases (e.g. CO). For this application various carriers are coated with precious metals.
Compound |
CAS Number | Formula | Metal Cont. approx. | Color |
---|---|---|---|---|
Platinum black, Pt | 7440-06-4 | Pt | 90-100 % | black |
Iridium black | 7439-88-5 | Ir | 98 % | black |
Platinum/Ruthenium black | 7440-06-4 /7440-18-8 | Pt/Ru | 25/75 % | black |
Gold black | 7440-57-5 | Au | 97 % | brown |