A depolarizer or depolariser, in electrochemistry, according to an IUPAC definition[1], is a synonym of electroactive substance, i.e., a substance which changes its oxidation state, or partakes in a formation or breaking of chemical bonds, in a charge-transfer step of an electrochemical reaction.

In battery industry, the term "depolarizer" has been used to denote a substance used in a primary cell to prevent buildup of hydrogen gas bubbles. [2]. Battery depolarizer takes up electrons during discharging the cell; therefore, it is always an oxidizing agent. The term "depolarizer" can be considered as outdated or misleading since it is based on the concept of "polarization" which is hardly realistic in many cases[citation needed].



Under certain conditions for some electrochemical cells, especially if they use an aqueous electrolyte, hydrogen ions can be converted into hydrogen atoms and H2 molecules. In the extreme case, bubbles of hydrogen gas might appear at one of the electrodes. If such a layer of hydrogen or even H2 gas bubbles appear on the positive plate of a battery, they interfere with the chemical action of the cell. An electrode covered with gases is called polarized. Polarization in galvanic cells causes the voltage and thus current to be reduced, especially if the bubbles cover a large fraction of a plate. Depolarizers are substances which are intended to remove the hydrogen, and therefore, they help to keep the voltage at a high level. However, this concept is outdated, since if enough depolarizer is present, it will react directly in most cases by getting electrons from the positive plate of the galvanic cell, i.e. there will be no relevant amount of hydrogen gas present. Therefore, the original concept of polarization does not apply to most batteries, and the depolarizer does not react with hydrogen as H2. Still, the term is used today, however, in most cases, it might be replaced with oxidizing agent.

Many different substances have been used as depolarizers; the most notable are listed below.

Oxidizing agents

These oxidize the hydrogen to water. Examples include:

Nitric and chromic acids are powerful oxidizing agents, and effective depolarizers, but their hazardous nature makes them unsuitable for general use. Manganese dioxide is, therefore, the most widely used depolarizer.

Salts of metals

The hydrogen ions displace metal from the salt so that metal, instead of hydrogen, is deposited on the positive plate. Examples:


  1. ^ Entries "depolarizer" and "electroactive substance" in "The IUPAC Compendium of Chemical Terminology", 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
  2. ^ "McGraw-Hill Dictionary of Scientific & Technical Terms", McGraw-Hill, Inc., 2003.
  • Everyman's Encyclopaedia, 1931, volume 3, pp. 520-522

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Look at other dictionaries:

  • Depolarizer — De*po lar*i zer, n. (Elec.) A substance used to prevent polarization, as upon the negative plate of a voltaic battery. [1913 Webster] …   The Collaborative International Dictionary of English

  • depolarizer — (Amer.) n. substance that removes polarity (also depolariser) …   English contemporary dictionary

  • depolarizer — depoliarizatorius statusas T sritis chemija apibrėžtis Medžiaga, mažinanti elektrodo poliarizaciją. atitikmenys: angl. depolarizer rus. деполяризатор …   Chemijos terminų aiškinamasis žodynas

  • depolarizer — depoliarizatorius statusas T sritis fizika atitikmenys: angl. depolarizer vok. Depolarisator, m rus. деполяризатор, m pranc. dépolarisant, m …   Fizikos terminų žodynas

  • Depolarizer (optics) — A depolarizer or depolariser is an optical device used to scramble the polarization of light. An ideal depolarizer would output randomly polarized light whatever its input, but all practical depolarizers produce pseudo random output polarization …   Wikipedia

  • depolarizer — noun see depolarize …   New Collegiate Dictionary

  • depolarizer — /dee poh leuh ruy zeuhr/, n. a substance added to the electrolyte of an electric cell or battery to remove gas collected at the electrodes. * * * …   Universalium

  • depolarizer — noun Any substance added to the electrolyte of a battery that produces hydrogen in order to combine with the liberated hydrogen and prevent the build up of pressure …   Wiktionary

  • depolarizer — de·po·lar·iz·er (de poґlər īz″ər) 1. a chemical agent placed in a galvanic cell for reducing the polarization of an electrode. 2. a substance that reduces the voltage across a biological membrane. 3. a muscle relaxant that… …   Medical dictionary

  • depolarizer — de·polarizer …   English syllables

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