An electrolyzer is an instrument used in electrolysis that splits water molecules into hydrogen and oxygen using electricity, thus producing hydrogen. There are several types of electrolyzers like PEM (Proton exchange membrane), and alkaline-based electrolyzers. They are known as a renewable source for clean energy. 
 

An electrolyzer consists of an anode (positive) and cathode (negative) called electrodes. These electrodes are separated by an electrolyte (the type of electrolyte varies). 

What is Electrolysis?

Electrolysis uses electric current and an electrolyzer to produce hydrogen. In the electrolysis process, electric current passes through an electrolyzer causing a chemical reaction that splits the electrolyte into protons and electrons.

The protons are attracted to the cathode, and the electrons to the anode producing two hydrogen and oxygen. 

Types of Electrolyzers

The electrolyzer types differ in size and usage, and the most common electrolyzer types are explained as follows: 

Types of Electrolyzer

Proton Exchange Membrane Electrolyzers (PEM)

PEM electrolyzers are known due to their high efficiency operating at lower temperatures, and rapid response time, ensuring reduced maintenance and energy consumption costs. 

Source: ITM Power PLC

In the PEM electrolysis, the electrodes are separated by a solid specialty plastic material. In the PEM electrolysis, water is oxidised at the anode producing oxygen and protons (Hydrogen ions). These positively charged hydrogen ions move through the PEM membrane from the anode toward the cathode, where they combine with the electrons to form hydrogen. 

Anode Reaction: 2H2O → O2 + 4H+ + 4e- 

Cathode Reaction: 4H+ + 4e- → 2H2

Alkaline Electrolyzers

Alkaline electrolyzers are the most commonly used in green hydrogen production plants, industrial processes such as ammonia production, steel making, and energy storage. 
 

 Source: LONGi

Alkaline electrolysers use sodium hydroxide (NaOH) or potassium hydroxide (KOH) as an electrolyte during electrolysis.

In alkaline electrolysis, NaOH (electrolyte) splits, forming Na+ sodium ions at anode and hydroxide ions (OH-) at cathode.

The hydroxide ions (OH-) move from cathode to anode, forming hydrogen gas on the cathode side.

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Solid Oxide Electrolyzer Cell (SOEC)

Solid Oxide Electrolyzers are most commonly used in high-temperature hydrogen production and are known as more efficient than PEM or Alkaline electrolyzers. 

Source: Sunfire GmbH

The SOEC (Solid Oxide Electrolysis cells) operates at high temperatures around 700°–800°C wherein the electrons from the external circuit combine with water at the cathode to form hydrogen gas and negatively charged oxygen ions. These oxygen ions pass through the solid ceramic membrane towards the anode to form oxygen gas.

Anion Exchange Membrane (AEM) Electrolyzer

AEM electrolyzers are known to produce high-quality hydrogen at lower costs compared to traditional PEM electrolyzers. It uses a semi-permeable membrane such that the hydroxide ions (OH-) pass from cathode to anode electrode forming hydrogen gas. 

What is a Green Hydrogen Electrolyzer?

A green hydrogen electrolyzer uses electricity to split water into hydrogen and oxygen. The electricity generated from renewable energy sources (wind and solar PV) to split water into hydrogen and oxygen. The hydrogen produced by electrolysis using renewable sources emits no carbon emissions. Thus, thsi carbon-free hydrogen production is called green hydrogen. The use of such sources for renewable electricity differentiates a green hydrogen (clean hydrogen) electrolyzer from a traditional electrolyzer.
 

Read: What is Green Hydrogen and its Benefits I Explained

Benefits of Green Hydrogen Electrolyzer

Zero Carbon-emissions: The use of renewable sources for electricity ensures there is no carbon emission during water electrolysis, making it environmentally-friendly compared to the traditional use of fossil fuels that produce gray hydrogen with large scale carbon emissions.

Stimulates Economic Growth: The renewable produced green hydrogen promotes export opportunities for the global green hydrogen market stimulating the global electrolyzer market stimulating economic growth.

Enhanced Energy Storage: Green hydrogen produced can be stored and transported easily making it a potential alternative to other forms of hydrogen. Additionally, it helps in producing electricity during peak demand.

Used in Multiple-forms:  Green hydrogen and its derivatives like hydrogen fuel cell, green ammonia and FCEV make it a potential renewable source of sustainable energy to improve air quality and reduce reliance on combustion based sources.

Top Electrolyzer Manufacturers in the World

• Longi
• Plug Power
• HyGreen Energy
• Bloom Energy

Read: Top 15 Hydrogen Electrolyzer Manufacturers (By Capacity)

Region-Wise Electrolyzer Market Analysis

According to Blackridge’s global electrolyzer market report, China is leading the electrolyzer market with a cumulative electrolyzer capacity of 1 GW where the world’s two largest operational projects with capacities of 260 MW and 150 MW are located as of Q4 2023. 

Likewise, Europe installed electrolyzer capacity as of 2023 end is 110 MW considering France and Germany. Germany has a cumulative electrolyzer capacity of 80 MW and France has cummulative electrolyzer capacity of 30 MW. 

The German government recently launched large-scale green hydrogen projects across Germany under the Energiewende- an energy transition plan. Similarly, Spain announced an increase in its electrolyzer capacity goals from 4 GW to 12 GW under the PNIEC (National Integrated Energy and Climate Plan 2023-2030). Under this, the Spanish government announced several green hydrogen projects across Spain.

Get complete insights and latest trends in the electrolyzer market through Blackridge’s global electrolyzer market report.

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Conclusion

An electrolyzer is an instrument that uses electrical energy that splits water into hydrogen and oxygen. There are several types of electrolyzers such as PEM electrolyzer, Alkaline electrolyzer, SOEC and Anion exchange membrane electrolyzer. Thus, with growing demand for green hydrogen several hydrogen policies are implemented boosting the green hydrogen market and the use of hydrogen electrolyzers.

FAQ’s

What is the difference between a fuel cell and an electrolyser?

A fuel cell uses hydrogen to produce heat and electricity, whereas electrolyzers use electrical energy to split water molecules and produce hydrogen and oxygen.

What are the three types of electrolysers?

PEM electrolyzers (Polymer Electrolyte Membrane), Alkaline electrolyzers, and SOEC (Solid Oxide Electrolyzer Cells) are three commonly known electrolyzers. 

What is the difference between an electrolyte and an electrolyser?

An electrolyzer performs an electrochemical reaction on a substance like water, acid, or base salt called electrolyte, which dissociates into positive and negatively charged ions.

What does electrolysis mean?

Electrolysis is a process that produces hydrogen by splitting water into hydrogen and oxygen by passing electrical energy through an electrolyzer.  

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