Electrolysis

Water + Electricity = Hydrogen

Hydrogen’s ability to combine with oxygen was first noted by Henry Cavendish in 1766. The first electrolyzer subsequently appeared in 1800 when Nicolson and Carlisle induced a static charge into water. More than 200 years later Hydrogenics continues to evolve and improve on these fundamental discoveries.

Electrolysis cells are characterized by their electrolyte type. There are two types of low temperature electrolysis where Hydrogenics is active: Alkaline and Proton Exchange Membrane (PEM).

Thanks to decades of research and development in both technologies, Hydrogenics has the unique capability to offer PEM and Alkaline systems and to select the most appropriate one based on the cost, capacity and use of it.

Both Alkaline and PEM technologies have the ability to deliver:

  • On site and on demand hydrogen (load following)
  • Pressurized hydrogen without a compressor
  • 99.999% pure, dry and carbon-free hydrogen 

Cathode reaction: 4H2O + 4e- → 4OH⁻ + 2H2 ↑
Anode reaction: 4OH⁻ → 2H2O + 4e- +O2 ↑
Overall reaction: 2H2O → 2H2 ↑ +O2 ↑

In alkaline electrolysis the reaction occurs in a solution composed of water and liquid electrolyte (30% KOH) between two electrodes. When a sufficient voltage is applied between the two electrodes, at the cathode water molecules take electrons to make OH⁻ ions and H2 molecule. OH⁻ ions travel through the 30% KOH electrolyte towards the anode where they combine and give up their extra electrons to make water, electrons, and O2

Recombination of Hydrogen and Oxygen at this stage is avoided by means of the highly efficient and patented IMET® ion-exchange membrane.  Our IMET® membrane is made of highly resistant inorganic materials and does not contain any asbestos. The electrolyte remains in the system due to a clever and pump-free closed-loop recirculation system.

Hydrogenics’ HySTAT® electrolysers are installed at hundreds of industrial plants, power stations, energy storage facilities and fueling stations around the world.  They are safe and reliable systems used by all major industrial gas suppliers in heavy-duty applications.   

pem-electrolysis-diagram
Anode reaction: 2H2O → 4H+ + 4e- +O2 ↑
Cathode reaction: 4H+ + 4e- → 2H2 ↑
Overall reaction: 2H2O → 2H2 ↑ +O2 ↑

A PEM electrolyser uses an ionically conductive solid polymer. When potential difference (voltage) is applied between the two electrodes, negatively charged Oxygen in the water molecules give up their electron at the anode to make protons, electrons, and O2 at the anode. The H+ ions travel through the proton conducting  polymer towards the cathode where they take an electron and become neutral H atoms which combine to make H2 at the cathode. The electrolyte and two electrodes are sandwiched between two bipolar plates. The role of bipolar plate is to transport water to the plates, transport product gases away from the cell, conduct electricity, and circulate a coolant fluid to cool down the process.

Same as fuel cells, many electrolyser single cells may be connected in series to make the core component of an electrolyser system, the cell stack, where both Hydrogen and Oxygen are produced.  

Cell Stack

Some cooling will be required to cool down the process and produced gas, a water treatment system will be installed in order to produce demineralized water from the supplied tap water, a purification system will clean the hydrogen to deliver high purity gas according to the customer’s specifications, a power rack will be installed to manage the power needed for the reaction (converting the AC current delivered by the grid into a direct current used for the process) and a control panel will allow the operator to have an overview of the complete package. All these wisely selected and specifically manufactured equipment will then either be installed in a building or packaged in an outdoor housing