Alkaline electrolysis, first observed on May 2, 1800, is a method of producing hydrogen by separating oxygen and hydrogen from water by an electric current in an alkaline solution.
The first water electrolysis (also the first method for producing hydrogen) was an alkaline electrolysis. On May 2, 1800, a few weeks after the invention of the battery by Alexandro Volta, William Nicholson and Sir Anthony Carlisle, reproduced the battery and immersed two copper wires connected to the battery in water. They observed “a small current of very fine bubbles from the tip of the copper wire communicating with the silver end of the battery”. This was the first electrolysis (which was also an alkaline electrolysis).
[Debate: according to Trasatti S. Water electrolysis: who first? Journal of Electroanalytical Chemistry Oct 1999;476(1):90e1. which is taken up by many, it is Troostwijk and Diemann who would have discovered the first in 1789].
We will study the principle of alkaline electrolysis, present some important dates of its evolution and finally we will study its practical dimensions (price, efficiency …).
The principle of alkaline electrolysis
The reaction occurring at the anode is the following:
2 OH− → H2O + 1/2 O2 + 2e−
The reaction occurring at the cathode is:
2 H2O + 2e− → H2 + 2 OH−
Here is a diagram. Note the diaphragm, permeable to water but impermeable to gas, which serves to separate the two gases:
The electrolyte is a liquid whose role is to serve as a “medium” for the reaction to take place.
It is in principle a solution of potassium hydroxide (potash, KOH) whose concentration varies according to the temperature (25% at 80°C to 40% at 160°C) (B.Guenot)
The problem of intermittency
One of the big problems of alkaline electrolysis is its inertia, which makes it (in principle) impossible to couple with intermittent energy.
“The inertia of the alkaline electrolyte, linked to the low mobility of the hydroxide ions and the high concentrations used, imposes the use of a stationary system for optimal performance. This system does not appear to be suitable for capturing intermittent energy.”
Guenot 2017
“Moreover, because of the use of a liquid electrolyte, this technique can hardly be coupled with an intermittent energy source (problems related to thermal management and the change in electrolyte conductivity during ramp-up in stop/start and load variation periods).”
Caroline Rozain 2013
Magnetic activation of alkaline electrolysis
One of the reasons alkaline electrolysis is not very compatible with intermittent energy is that the system must remain at 80°C.
To address this problem, researchers at LEPMI (Laboratory of Electrochemistry and Physicochemistry of Materials and Interfaces) have very recently (2018) developed “magnetic activation”.
This would consist in targeting the heating of the electrolyzer where it is needed using a magnetically sensitive material, which would heat up when immersed in a magnetic field. This is a bit like the microwave principle.
“We have therefore developed a catalyst composed of iron carbide nanoparticles coated with a layer of nickel. This architecture makes it possible to heat the core of the catalyst, the nature of which is chosen according to the maximum temperature that we wish to reach, and thus to reach a controlled temperature on the surface of the catalyst that is much higher than in conventional electrolysis.”
Marian Chatenet, researcher at LEPMI
Here is the diagram:
A demonstrator, carried out with the support of the Engie group, has already provided a proof of concept. The ANR Hy-walHy project aims to prepare an industrial production of the process.
History of alkaline electrolysis
Technological milestones
The discovery
- May 2, 1800: Discovery of alkaline electrolysis by William Nicholson and Sir Anthony Carlisle.
- End of May 1800: Humphry Davy describes the variations of acidity and basicity near the electrodes in a paper on the electrolysis of water.
- 1833: Michael Faraday, a student of Davy, discovers the Faraday constant, with a value of 96,500 coulombs. He also fixes the electrochemical nomenclature: electrolyte, electrodes, anode, cathode, ions, cations and anions. (only that!) Johan Hittorf
- 1884: Svante Arrhenius publishes the Chemical Theory of Electrolysis,
First patents
- November 20, 1888: Deposit of the first patent on the electrolysis of water by Latchinoff, adviser of State in Saint-Petersburg. He already had the principle of the diaphragm and electrolysis under pressure.
- 1889: Hermann Nernst discovered the “Nernst formula”, from which the famous pH scale was deduced, as well as the theoretical voltage of water decomposition (1.23 volts) by Haber.
- October 18, 1890: Filing of the second patent by Charles Renard on “monopolar cylindrical cells of 3.5m height, 300 mm diameter, with iron electrodes, of unitary power 0.81kW (2.7 V under 300A)”.
- 1892: Filing of the third patent by the Italian P.Garuti whose idea is to use the water electrolysers to recover the energy available in off-peak hours. They would act as “regulators”.
- 1899: Patent of a water electrolyser of the “filter press” type (“Schmitt model 1899”; “Oerlikon model”). After being sold to an industrialist, the model was a rapid commercial success, selling 400 units (power 2 to 38 kW) in 20 years.
Industrial developments
- 1920’s: Development of the Pechkranz electrolyser, which will replace the Oerlikon model. The largest models can have a maximum power of 875 kW. Nickel-sulphur activation
- 1925-1940: First unsuccessful attempts at pressure electrolysis by Noggerat and Neiderreiher Lawaczech.
- 1942: Development of PTFE by Du Pont de Nemours
- 1951: Zdansky develops a prototype for the Swiss company Lonza, with 25 cells of 1.6 meters in diameter, 13mm thick and operating at 30 bars.
- 1955: First large-scale pressurized electrolysis installation in Peru, with 27.2MW.
- 1978: Date when Alsthom, Creusot-Loire and CEM presented a project for an advanced smelter (= higher temperature / pressure) of 300MW in 1978. They will present projects operating at 120-140°, 160-180° and 200°C respectively.
- 2018: Development of magnetic activation of alkaline electrolysis.
Industrial history of alcalin electrolysis
First plants
- 1900: 6 plants of P.Garuti’s electrolyzer model are operating in Europe (4m3/hour for the one in Lucerne, Switzerland), mainly to supply the needs of the oxhydric welding.
- 1912: first large installation of monopolar cells (“Knowles Cell”), in particular to meet the needs of the development of hydrogenation of fats. They sold a total of 205 MW of these same models between 1922 and 1972.
- 1913: Industrial application of the Haber-Bosch process (production of ammonia from hydrogen and nitrogen, to make synthetic fertilizers), which will increase the need for dihydrogen. Even today, this is the main use of hydrogen.
- 1910s: Pioneers of the ammonia industry, Casale and Fauser, develop numerous water electrolysis units (>99MW).
Increase in power
- 1926-1927: 176 MW of Pechkranz electrolysers are installed.
- 1927: The company Norks-Hydro installs 120 MW of Pechkranz electrolysers in Vemork, Norway. The site will make history in two respects: its power (300MW) was still unequalled in 1996 and the plant was a stake in the “Battle of Heavy Water” in 1944-45.
The end of the war and the appearance of reformation
- The end of the war led to the development of many large installations (Norway: 165 and 40MW by NorskHydro; Nangal in India: 210MW by De Nora; Aswan in Egypt 200MW by Demag). However, the development of gasification and hydrocarbon reforming suddenly shrinks the market.
- 1970’s: Development of research for an advanced electrolysis in France, driven by EDF and the will to have an energy vector to optimize/regulate the electrical network. Nevertheless, the project aborted in the 90’s because of the competition of fossil hydrogen:
“The immediate and prospective technical and economic assessment made at the end of 1994 is gloomy for the foreseeable development of the sector in the French context. Only a strong and generalized taxation of the fossil CO2 discharge in the atmosphere appears to be able to bring the various manufacturing processes up to standard (typically a tax of the order of 50 $/tonne of CO2 such as it starts to be taken into account in certain countries). For these reasons, the decision was made to stop the current development. The dismantling of the Pont-de-Claix and Wazier test units began in early 1995.
Christian Bailleux
Practical dimensions of alkaline electrolysis
Alkaline electrolysis is the most mature form and does not require expensive materials.
Innovations
The sHYp (alkaline?) electrolyser would allow to produce hydrogen from sea water or brine
- without using a membrane
- by being adapted to intermittence
- by consuming 50% less energy (compared to … ?)
I am very dubious of these claims, the startup being very imprecise in its video and not talking at any time about its process.