Exploring the Basics of Hydrogen Electrolysis

One of the key methods for hydrogen production is water electrolysis. In this article by Stargate Hydrogen, a producer of next-generation green hydrogen electrolysers, we’ll explore the various methods used for water electrolysis.

What is electrolysis?

‘Water electrolysis’ is sometimes incorrectly referred to as ‘hydrogen electrolysis’. Water electrolysis is the process of splitting water (H20) into its constituent elements, hydrogen (H2) and oxygen (O2), using an electrical current. It is important to emphasise that ‘water electrolysis’ is the correct term, not ‘hydrogen electrolysis, since it is the H20 molecule that is electrolysed, not the H2 molecule.

Water electrolysis is performed through the use of an electrolyser, a device that contains two electrodes and an electrolyte separating them. When an electrical current is applied between the electrodes, water molecules are separated into hydrogen and oxygen gases.

Image ©Stargate Hydrogen

The main methods of Hydrogen Electrolysis

There are three prominent methods of water electrolysis:

• Alkaline electrolysis

• Proton Exchange Membrane (PEM)

• Solid Oxide Electrolyser Cell (SOEC)

Alkaline Electrolysis

Alkaline electrolysis is the method chosen by Stargate Hydrogen for its proven track record of reliability and its untapped potential. The technology is one of the most established methods of hydrogen production. Alkaline electrolysis is a process that involves splitting water molecules into hydrogen and oxygen using an alkaline electrolytic cell. This method uses an alkaline electrolyte solution, typically potassium hydroxide (KOH) or sodium hydroxide (NaOH), which acts as a conducting medium to facilitate the flow of ions between electrodes.

Proton Exchange Membrane

Proton Exchange Membrane (PEM) hydrogen electrolysis, is another method used for splitting water into hydrogen and oxygen. The PEM electrolysis cell consists of two electrodes, an anode and a cathode, separated by a solid polymer electrolyte membrane, typically made of a specialised proton-conducting material like Nafion. The anode and cathode are usually made of precious metals such as platinum, but efforts are ongoing to develop more cost-effective alternatives.

The solid polymer electrolyte membrane used in PEM electrolysis plays a crucial role by allowing the passage of protons (H+ ions) while preventing the mixing of hydrogen and oxygen gases. This design ensures the selective separation of the generated gases and minimizes crossover, improving the efficiency of hydrogen production.

The PEM electrolyser is compact and best suited for small-scale applications.

Solid Oxide Electrolyser Cell

Solid oxide electrolyser cell (SOEC) electrolysis, is a process that uses a solid oxide electrolyte to split water into hydrogen and oxygen gases at elevated temperatures. This technology is similar to solid oxide fuel cells (SOFCs) but operates in reverse to generate hydrogen instead of electricity.

In a solid oxide electrolysis cell, the cell itself consists of three main components: an electrolyte, an anode, and a cathode. The electrolyte is a solid oxide material, such as yttria-stabilised zirconia (YSZ) or ceria-based materials, which conducts oxygen ions (O2-) at high temperatures (typically above 700 degrees Celsius).

The anode and cathode are porous electrodes that facilitate electrochemical reactions. The anode is usually made of nickel-based materials, while the cathode can be composed of perovskite-type oxides or other mixed ionic-electronic conducting materials.

Solid oxide electrolysis operates at high temperatures, which enables faster ion transport through the solid electrolyte, enhancing the overall efficiency of the process. Additionally, the high operating temperatures allow for the utilisation of waste heat from industrial processes or other sources, increasing the overall energy efficiency.

The Advantages of Alkaline Electrolysis

Among the various hydrogen electrolysis methods, alkaline electrolysis stands out as a preferred choice for many industries. Alkaline electrolysis is favoured, particularly for industries like glass and ceramics, concrete production, steelmaking, and fertilisers due to:

• Efficiency: Alkaline electrolysis is known for its high efficiency, making it an economically viable option for large-scale industrial applications. The process converts a significant portion of the electrical energy into hydrogen gas.

• Durability: Alkaline electrolysers have a proven track record of durability and can operate continuously for extended periods. This is crucial for industries with continuous production processes.

• Mature Technology: Alkaline hydrogen electrolysis has been in use for decades. This means that companies can rely on established systems with a history of successful performance.

• Economic Viability: The relatively low cost of alkaline electrolysers, especially when produced at scale, makes them an economically attractive choice for industrial applications.

• Flexibility: Alkaline hydrogen electrolysis systems are adaptable and can be integrated into existing industrial processes, minimising the need for major infrastructure changes.

Conclusion

As the industrial landscape evolves to meet the demands of sustainability and environmental responsibility, hydrogen electrolysis, particularly the alkaline electrolysis method, remains consolidated as the main choice for industrial-scale hydrogen production. Companies in industries like glass and ceramics, concrete production, steelmaking, and fertilisers are increasingly recognising the importance of green hydrogen as a sustainable alternative fuel to reduce carbon emissions.

To find out more about Stargate Hydrogen, visit www.stargatehydrogen.com.