...from the electrolysis of water [ Return towards  Its production  ]

During a physics course, the teacher often shows the release of small gas bubbles around two electrodes (anode and cathode) connected to a cell submerged in saltwater. This is the electrolysis of water, a reaction known since 1800, which consumes electricity to produce hydrogen and oxygen.

At the anode (electrode connected to the negative pole), oxygen is released and at the cathode (electrode connected to the positive pole), the hydrogen produced will be recovered.

The reactions that take place are as follows:

At the anode: 2H₂O → O2 + 4H⁺ + 4 electrons

At the cathode: 4H₂0 +4 electrons →  2H₂ + 4OH^-

Which gives: 2H₂0 →  2H₂ + O₂

This production technique does not directly release CO₂. But in a global calculation, the production of electricity must be taken into account. If the electricity used is produced from a power plant, fueled by coal, for example, CO₂ will be emitted. If electricity is produced without emitting CO₂ (renewable or nuclear energy), the hydrogen produced is said to be “green”.