A (Brief) History of Electrolysis

The science that's reshaping industry, one molecule at a time.

By Nora Buggy, Staff Engineer and Dino Klotz, Senior Staff Engineer

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The Importance of Electrolysis | Why it Matters

Picture this: a world without aluminum - no soda cans, lightweight cooking pans, electricity cables, or commercial airplanes. Pure aluminum metal is just one of the many benefits society has reaped from the discovery of electrolysis chemical reactions.

Electrolysis is a cool technology because it is able to provide high-purity products with high energy efficiency, such that the aluminum for our soda cans don't crack and our airplanes are safe.

However, it is not only metals that can be produced by electrolysis. The Chloralkali process is another prominent example, where useful chemicals (chlorine and caustic soda) are produced from abundant precursors (salt/brine) by electrolysis. However, most people might associate electrolysis with water electrolysis for hydrogen production, which has a 14 billion USD global market size and is growing rapidly.

Early Developments | From Humble Beginnings

One of the first documented examples of utilizing an electrolysis reaction was by the Dutch scientist Martinus van Marum in 1785, who obtained pure metals (tin, zinc, and antimony) from their salts[1]. These early experiments paved the way for industrially scaling electrolysis reactions, enabling the purification of aluminum ore into more valuable and useful aluminum metal, along with many other metals we use every day.

Water electrolysis reactions were first performed in 1789 by Adriaan Paets van Troostwijk and Johan Rudolph Deiman. They used an electrostatic generator and gold electrodes to apply electricity to water[2], and watched as the water bubbled and fizzed. They discovered water could be turned into something else—hydrogen and oxygen gas—just by adding electricity. Following Alessandro Volta’s development of the first battery, the voltaic pile, in 1800, English scientists William Nicholson and Anthony Carlisle would repeat these experiments with this more reliable and inexpensive electricity source. Together, Nicholson and Carlisle were able to analyze the products of this reaction separately, and also noted the formation of solid products in addition to gaseous ones[3]. The question of who invented electrolysis remains a subject of considerable debate[4]. While Volta likely discovered electrolysis first, he did not take note nor particular interest in the electrochemical conversion processes related to his battery.

Early water electrolysis experiment in a laboratory, 1864, from Zöllner [5]

Electrolysis is a type of electrochemical reaction - a chemical reaction that involves either the production or consumption of electricity. An electrochemical reaction consists of two half-reactions, one requiring one or more electrons, and the other freeing up one or more electrons. If those reactions are spatially separated, the electrons can be used in an outer circuit, such as in a fuel cell or a battery. In the case of electrolysis, an external circuit is used to drive the reaction.

In essence, every chemical reaction has that electrical component, since a chemical reaction involves the rearrangement of electrons. However, in most chemical reactions, substances are not separated, and the reaction is performed spontaneously and uncontrolled. That means for exothermic reactions (releasing energy, think of burning) that those electrons cannot be captured, and the electricity cannot be used - rather, the corresponding energy is released as heat. For endothermic reactions (consuming energy), energy has to be invested to drive the chemical reaction, and this is mostly done by providing heat rather than by using electricity, because there is no ordered reaction pathway, and actually designing the cell and electrodes is not trivial.

Specifically, electrolysis refers to using electricity (‘electro-’)  to break molecules into smaller components (‘lysis’ means to separate or break). Nicholson and Carlisle demonstrated how water (H₂O) could be broken down into molecules of hydrogen (H₂) and oxygen (O₂), similar to how Marum (accidentally) split tin salts into pure tin metal and chlorine gas.

Routes of water electrolysis (top) and production of pure metals from ore through electrolysis (bottom).

It was not until 1834 that Michael Faraday published the laws of electrolysis and provided a more thorough mathematical explanation[6]. He introduced new terminology that is commonly used today, including electrodes and electrolytes, anodes and cathodes, and anions and cations. 

Examples of electrolysis reactions, including terminology introduced by Michael Faraday. Above: Tin purification via electrolysis, a model example of metal purification, first demonstrated by Martinus van Marum. Below: Water electrolysis, a method of producing hydrogen and oxygen from water. The electrodes are the anode (positive electrode) and the cathode (negative electrode), cations (positive ions) and anions (negative ions) are labeled for each reaction, and the electrolyte is typically a salt solution that the electrodes are immersed in. 

The Power of Electrolysis | Transforming the Industrial Landscape

From that point forward, much of the progress in the field of electrolysis focused on developing new processes for purifying metals and other essential feedstock molecules. One of the first larger-scale applications of water electrolysis was by Charles Renard, who constructed a water electrolysis unit to generate hydrogen for airships in the French military in 1890[7]. By the early 1900s, industrial chlor-alkaline electrolyzers were in operation globally. In this process, brine (i.e. salt water, an aqueous solution of NaCl) is electrochemically split to produce caustic soda (i.e. sodium hydroxide, NaOH), along with hydrogen and chlorine gas. In early applications, the hydrogen produced was not utilized and was often vented to the atmosphere. Caustic soda was mainly used in soap and detergent production, as well as in paper and textile processing. 

Schematic of one of Charles Renard’s hydrogen production units, from 1888 [7]

Later, different types of commercial alkaline water electrolyzers were developed in the 20th century to produce the hydrogen needed in the Haber-Bosch process for ammonia-based fertilizers. Eventually, hydrogen production became more cost-effective via a new process known as methane steam reforming, which largely replaced industrial alkaline water electrolysis. Today, methane steam reforming remains the primary method for industrial hydrogen production. 

Reigniting Interest in Industrial Water Splitting | The Proton Exchange Membrane

Renewed interest in industrial water electrolysis came with the development of the proton exchange membrane (PEM), specifically Nafion®, developed at DuPont by Donald J. Connolly[8]. The PEM was originally developed to create a more efficient and compact fuel cell, which carries out the opposite process of an electrolyzer. Fuel cells combine hydrogen and oxygen to generate electricity and water, while electrolyzers use water and electricity to produce hydrogen and oxygen. 

The invention of the PEM ushered in a new era for water electrolysis, replacing bulky, large volumes of liquid electrolyte with an ultra-thin polymer sheet. Water electrolysis using PEMs started in the late 1960s within the Russell, Nuttall, and Fickett research group at General Electric[9]. At the time, their work was mainly focused on developing this technology for oxygen generation for the Space Program. In fact, a PEM water electrolyzer is currently used on the International Space Station to produce oxygen for astronauts.

Left: 2.5 ft² solid polymer electrolysis membrane/electrode assembly from GE, from [10]. Right: >700 cm2 membrane electrode assembly from Twelve. Source:Twelve.

These innovations led to improvements in the design and efficiency of the water electrolysis process, eventually bringing in a new competitor for methane steam reforming for hydrogen production. PEM water electrolyzers can typically reach efficiencies of 80%, which makes electrolysis an industrial process with little waste[11]. More recently, climate protection agreements and requirements to reduce greenhouse gas emissions have sparked renewed interest in water electrolysis as a cleaner alternative to steam methane reforming, which relies on fossil fuels, produces high carbon dioxide emissions, and is quite energy-intensive. Instead, there are efforts to utilize hydrogen as a fuel, and to couple water electrolyzers with renewable or nuclear power sources (known as Power-to-X technologies, where X can be gas, heat, liquid fuel, etc). Essentially, excess energy (‘power’) generated by renewable sources can be transformed into hydrogen via water electrolysis, or other chemicals and fuels (‘X’), which are easier to store and utilize. 

It is worth mentioning that there exist other technologies for water electrolysis, such as solid oxide electrolyzer cells (SOEC) that operate at temperatures >500 °C; with the higher operating temperature comes a higher technically achievable efficiency, but also challenges for operation [12].

Current Research Trends | Where Twelve is Making History

There are still many emerging areas of electrolysis research and development, including seawater electrolysis, iron ore electrolysis, and electrolysis of carbon dioxide - this is where Twelve enters the history books.

Carbon dioxide (CO2) electrolysis can be extremely valuable because it converts CO2 - the most abundant greenhouse gas causing global warming - into a valuable product. This product is carbon monoxide (CO), a gas often recognized for its toxicity, but which is also a building block for producing almost anything carbon-based: think fuels, plastics, and other materials. (See CO2Made®).

Currently, there is no commercially available system for CO2 electrolysis on the market. Direct CO2 electrolysis is one of several methods for producing CO for sustainable aviation fuel (SAF). A handful of companies are in the demonstration phase, with Twelve being one of the leading innovators in this field. 

At Twelve, we are focused on scaling our CO2 electrolyzer, called the Opus System. The Opus System is about the size of a shipping container - it houses the CO2 electrolyzer stack, along with all of the plumbing and sensors to deliver CO2 and water to the stack, and remove our product CO. 

These developments start at the lab scale, where we (the authors) work. We study and optimize the CO2 electrolysis process with sub-scale reactors with a much smaller active area scale, constantly improving the device's performance through material and operational developments. 

Left: Stack assembly, >700 cm2 active area per cell. Right: Subscale reactor assembly, 25 cm2 active area. Source: Twelve.

We also work on translating what we learn about our sub-scale system to our tall stacks. These systems, like those found in Opus, consist of much larger active areas (think >700 cm2) with many cells (>50) stacked on top of each other. Over the past 2-3 years that we have both worked at Twelve, we’ve scaled our electrolyzer active area and nearly tripled our performance metrics - increasing our operating current density, efficiency, and device longevity. It's an exciting time to be a part of history.

An Optimist's Guide to the Planet goes inside Twelve's Lab.

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References

[1] The Supplement (1803 edition) to Encyclopædia Britannica 3rd edition (1797), volume 1, page 225, "Mister Van Marum, by means of his great electrical machine, decomposed the calces of tin, zinc, and antimony, and resolved them into their respective metals and oxygen" and gives as a reference Journal de Physiques, 1785.

[2] A.P. van Troostwijk, J.R. Deiman, Lettre à M. de la Mètherie, sur une manière de dècompose l’eau en air inflammable et en air vital, Journal de physique, de chimie et de l’histoire naturelle 35 (1789) 369–378.

[3] W. Nicolson, Account of the new Electrical or Galvanic Apparatus of Sig. Alex. Volta, and Experiments performed with the fame, Nicholson’s Journal of natural philosophy, chemistry and the arts 4 (1800) 179– 187.

[4] S. Trasatti, Water electrolysis: who first? J. Electroanal. Chem. 476 (1999) 90–91. https://doi.org/10.1016/S0022-0728(99)00364-2.

[5] J. Zöllner, E. Bobrik, F. Ahrens, H Wagner, Das neue Buch der Erfindungen, Gewerbe und Industrien. In: Rundschau auf allen Gebieten der gewerblichen Arbeit: Die Kräfte der Natur und ihre Benutzung. Eine physikalische Technologie. mit drei Tonbildern, über 450 Text-Illustrationen, sowie einem Titelbilde, Verlagsbuchhandlung Otto Spamer, Leipzig, 1864

[6] M. Faraday, Experimental-Untersuchungen über Elektrizität (1834): VII. Reihe, Von der elektrochemischen Zersetzung, Ostwalds Klassiker der exakten Naturwissenschaften 87 (1897) 39–106.

[7] V. Engelhardt, Monographien über Angewandte Elektrochemie. I. Die Elektrolyse des Wassers, ihre Durchführung und Anwendung, Verlag von Wilhelm Knapp, Halle (1902).

[8] Connolly D.J., Gresham, W.F., Fluorocarbon vinyl ether polymers. US Patent 3282875A, 1964.

[9] J.H. Russell, L.J. Nuttall, A.P. Fickett, Hydrogen generation by solid polymer electrolyte water electrolysis, Am. Chem. Soc. Div. Fuel Chem. Preprints 18 (1973) 24–40.

[10] L.J. Nuttall, J.H. Russell, Solid polymer electrolyte water electrolysis — development status, Int. J. Hydrog. Energy 5 (1980) 75–84. https://doi.org/10.1016/0360-3199(80)90116-0.

[11] M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, A comprehensive review on PEM water electrolysis, Int. J. Hydrog. Energy 38 (2013) 4901-4934. https://doi.org/10.1016/j.ijhydene.2013.01.151

[12] W. Sitte, R. Merkle (editors), High-Temperature Electrolysis: From Fundamentals to Applications (IOP Publishing Ltd), 2023. ISBN 978-0750339490