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Electrolysis

Electrolysis is chemical decomposition produced by passing an electric current through a liquid or solution containing ions.

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What is Electrolysis?

Electrolysis is the process by which ionic substances are decomposed into simpler substances when a direct electric current is passed through it. The key process of electrolysis is the interchange of atoms and ions resulting in the removal or addition of electrons1.

Electrolysis is commonly used in energy for the production of hydrogen. Electrolysis uses direct current (DC) electricity to split water into its basic elements of hydrogen and oxygen. Since this process uses only water as a source, it can produce up to 99.9995% pure hydrogen and oxygen.

The main components required for electrolysis are:

  • An electrolyte
  • A direct current (DC) supply
  • Two electrodes

During electrolysis, positively charged ions move to the negative electrode. They receive electrons and are reduced. Similarily, negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised. The substance that is broken down is called the electrolyte2.

There are currently different types of electrolyzers, the most common being:

  • alkaline and proton exchange membrane
  • solid polymer electrolyte membrane

Hydrogen through water electrolysis requires a significant amount of energy. Research by the National Renewable Energy Laboratory (NREL) indicates 39 kWh of electricity and 8.9 liters of water are required to produce 1 kg of hydrogen1.

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Electrolysis requires a large amount of energy and, as a result, is not a common method used by industry to produce hydrogen. However, electrolyzers are still used in places where low electricity prices are available or that have high hydrogen purity requirements.

 

 

 

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  1. B. Kroposki, J. Levene, K. Harrison, P.K. Sen, F. Novachek (2006). Electrolysis: Information and opportunities for electric power utilities.
  2. BBC (2014). Electrolysis. http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electrolysis/electrolysisrev1.shtml
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