Electrochemistry

Electrochemistry referred to several different sub-areas within chemistry. It is partly as a method of synthesis, preparative electrochemistry or electrolysis or electro synthesis, on the other hand it is a branch of physical chemistry, which deals with the relationship between electrical and chemical processes. Furthermore, there are electrochemical methods in analytical chemistry. The Technical Chemistry knows next to a large scale applied electrochemical synthesis methods nor the battery and fuel cell technology and electroplating.

Content

If a chemical reaction with an electrical current is associated, this is an electrochemical process. The redox reaction is either an externally applied electrical voltage forced ( electrolysis), or it is caused by the chemical reaction of appropriate substances, a measurable voltage ( galvanic element ). These tensions are characteristic of the respective reactions have been documented on a scale of the electrochemical series. The direct electron transfer between molecules, ions or atoms is not an electrochemical process; typical of the electrochemistry is the spatial separation of oxidation and reduction.

Electrochemical reactions take place in a galvanic cell and always as redox reactions. During the electrolysis, and the charging of a storage battery while power is supplied to the discharging of the battery or current consumption is obtained from a fuel cell electric energy corresponding to the enthalpy of reaction for the reversible processes.

The current occurring in such reactions is an easy to be detected characteristic which is very valuable for monitoring. It is often incorporated a current-voltage characteristic curve, which represents variation in the measured current of the voltage. The shape of such a curve depends not only on the usual reaction parameters (concentration of the substances involved, temperature, size of the reactive interfaces) also on the rate of voltage change from.

The key for electrochemistry redox processes during these processes at the interface electrode - electrolyte. One can therefore define: Electrochemistry is the science of the processes at the phase boundary between an electron conductor ( electrode) and an ionic conductor (electrolyte).

History

An important impetus for the development of electrochemistry was the attempts by Luigi Galvani with frog legs: the muscles contracted when they were in contact with various metals. Alessandro Volta in 1799 presented the first working battery of the modern era ago. This was - long before the development of the generator - an extremely important current and voltage source, which enabled many significant discoveries, especially the first-time presentation of the metals sodium, potassium, barium, strontium, calcium and magnesium in the years 1807 and 1808 by Humphry Davy.

Johann Wilhelm Ritter delivered late 18th century, important contributions on the subject of galvanism and constructed a simple accumulator. Michael Faraday, who introduced the concepts of electrode, electrolyte, anode, cathode, anion and cation, discovered in 1832 the basic laws of electrolysis. In 1959 Jaroslav Heyrovský received for the development of an electrochemical method of analysis, polarography, the Nobel Prize for Chemistry.

Already in the years 1887/1894 Wilhelm Ostwald recognized that effective fuel cells for energy supply would provide a huge potential for the future. Among the important developments of the 20th century, accordingly, includes the development of the fuel cell, initially primarily for applications in space: For the Apollo program, which led to the 1969 moon landing, hydrogen fuel cells have been developed that also provided potable water for the astronauts. Even the Space Shuttle served hydrogen fuel cells for power.

Applications

  • Production of chemical substances Reduction of metal salts for the production of base metals, especially by melt electrolysis, eg for the preparation of lithium, sodium, potassium, calcium, magnesium and aluminum The electric current acts as a reducing agent. Since the voltage can be varied, the reduction force can be adjusted. The electric current is the strongest of the chemical reducing agent, with the cations of the least noble metals can be reduced. The electrolytic deposition of metal is also used in electroplating.
  • Oxidation of anions, such as halides, for example for the production of fluorine and chlorine in the chlorine -alkali electrolysis,
  • The electric current allowed redox reactions without the addition of reducing or oxidizing agents. Many other redox reactions can therefore be carried out electrolytically particularly elegant or be possible at all. Be mentioned in preparative organic electrochemistry electrofluorination, the dimerization of acrylonitrile to adipodinitrile or the Kolbe electrolysis. Formerly also been electrochemical Grignard reaction for preparing tetraethyl important.
  • Production of ozone in Siemens'schen ozonizer
  • Providing an electrical voltage, particularly for mobile applications, in Galvanic cells ( D-cells )
  • Battery
  • Accumulators
  • Fuel cells
  • Use of the electric current and measurement of the potential in the performance of chemical analysis and testing: electroanalysis, especially Voltammetry / cyclic voltammetry
  • Polarography
  • Amperometry
  • Potentiometry
  • Coulometry
  • Electrogravimetry
  • Studies with ion-selective electrodes
  • Electrochemical impedance spectroscopy
Standard electrode potential (data page) History of electrochemistry Humphry Davy Salt (chemistry) Aluminium Electrochemical fluorination Product (chemistry) Double layer (interfacial) Photoelectrochemistry Nernst equation Butler–Volmer equation Tafel equation Biochemistry Bioinorganic chemistry Biogeochemistry Biophysical chemistry Chemometrics Femtochemistry Geochemistry Nuclear chemistry Clinical chemistry Interface and colloid science Combinatorial chemistry Magnetochemistry Medicinal chemistry Marine chemist Quantum chemistry Stereochemistry Thermochemistry Integrated Authority File
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