How does a hydrogen electrolyzer work?

Posted: May 03, 2024

Hydrogen is getting a lot of buzz as an amazing sustainable fuel. But, if you’re going to use hydrogen as fuel, you first have to get it from somewhere.

Luckily, hydrogen is the most abundant element in the universe—and one component of everyone’s favorite drink: water. Each molecule of water—H₂O—just is two hydrogen atoms and one oxygen atom.

One of the most popular ways of getting hydrogen is using electricity to split those water molecules apart into their hydrogen and oxygen constituents. That process is called electrolysis. Electrolyzers are the mechanisms that carry it out.

Three basic components

All electrolyzers have three basic components: an anode and a cathode separated by an electrolyte. Exactly how these components work together to split water into hydrogen and oxygen depends on what materials they’re made of. Here’s how the process [AK1] works for one popular kind of electrolyzer: a polymer electrolyte membrane (PEM) eclectrolyzer^[i]:

Anode The anode—often iridium or ruthenium oxide^[ii]—catalyzes a reaction in which water splits into oxygen gas as well as both positive hydrogen ions (protons) and electrons. The oxygen gas gets released as a byproduct while the electrons flow through an external electrical circuit. Meanwhile, the positive hydrogen ions travel through the electrolyte.

Electrolyte In the case of a PEM electrolyzer, the electrolyte is a plastic membrane engineered to pass the hydrogen ions generated at the anode on to the cathode.

Cathode The cathode—often platinum or palladium—collects the positive hydrogen ions coming from the electrolyte along with the electrons that have travelled through the electrical circuit from the anode. It catalyzes a reaction combining the positive hydrogen ions with the electrons to produce hydrogen gas.

Sustainability

The whole process described above relies on an external power source to generate the electrical current that carries the electrons. So, how sustainable electrolysis is depends on how sustainable the electricity powering it is.

Industry has given different color names to the hydrogen produced by electrolyzers that indicate how sustainably they’ve been powered. For example, green hydrogen comes from electrolyzers powered by sustainable sources like solar and wind, whereas pink hydrogen comes from electrolyzers powered by nuclear. Check out my previous blog here on the different colors of hydrogen for a deeper dive into this topic.

How data helps

Where does AVEVA fit in to the hydrogen picture? Its solutions help companies collect, organize and analyze data so they can engineer, operate and optimize electrolyzer technology efficiently.

• Check out this infographic to learn more.
• For example, Topsoe will use AVEVA™ Process Simulation to model its solid oxide electrolyzer cells (SOECs) with a view to optimizing their design and developing their control strategy. Learn more.
• Download this free white paper to discover what factors are driving investment in hydrogen technology and the digital strategies you need to meet the growing hydrogen economy head-on.

^{[i] https://www.energy.gov/eere/fuelcells/hydrogen-production-electrolysis
[ii] https://www.sciencedirect.com/science/article/pii/S2589299119300035#s0030}