Electrolysis of Water 3

A hand-held voltage generator is used to convert mechanical energy ito electrical energy to electrolyze water into hydrogen and oxygen gases.

Equipment

  • electrolysis apparatus (see photos)

Presentation

  1. The electromagnetic voltage generator is shaken to move the magnet through the wire coil and generate an electrical voltage. 
  2. The voltage is shown on the meter with a document camera.
  3. The bubbles forming on the platinum wires are also shown on the document camera.

Details

A minimal voltage of 1.23 V is needed to drive the oxidation (although normally an overpotential of 6-8 V is needed to achieve reasonable kinetics for the oxygen half reaction).  This is easily achieved with the hand-held voltage generator, leading to hydrogen bubble formation on one platinum electrode and oxygen bubbles on the other.

Interestingly, when the demonstrator stops shaking the generator, a small voltage will persist for some seconds as the oxygen and hydrogen bubbles on the wires are converted back to water (as in a fuel cell).  

Safety

explosion

Special Safety Notes

  • hydrogen and oxygen gases are generated in this demo, keep away from open flames.
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Side view of the electrolysis apparatus.
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The residual voltage measured on the meter as the hydrogen and oxygen bubbles are reconverted back to water.
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Top down view of apparatus showing the hand-held electromagnetic voltage generator.
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Close up of platinum wires with hydrogen and oxygen bubbles forming.