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Proton exchange membran (PEM) water electrolysis for green hydrogen production

Advance your production of hydrogen with Hybrion PEM electrolysis stacks and services by Bosch.

3D graphic of a future hydrogen ecosystem with Bosch PEM electrolyzers and renewable energy sources

Hydrogen produced via the proton exchange membrane electrolysis (PEMEL or PEM) method is one of the key elements of a low emission energy economy. It is generated in electrolysis systems powered by electricity with water as the raw material. The reaction products of this electrochemical process are hydrogen and oxygen.

Hybrion PEM electrolysis stacks

Our contribution – Hybrion PEM Electrolysis Stacks

With the Hybrion PEM electrolysis stacks, we deliver the heart of your hydrogen production. Our many years of experience in industrialization and automation will be incorporated into the production of the Hybrion stacks, of course, with the excellent Bosch quality you expect.

Our goal is to provide you with a scalable solution for global hydrogen generation. With our advanced electrolysis technology and accompanying services, we intend to pave the way for a future-proof energy system that reduces CO₂ emissions – thus protecting the world for both present and future generations.

Find out more about our Hybrion PEM electrolysis stacks here:

Green hydrogen – an all-rounder in the energy system

Green hydrogen is generated in electrolysis systems using water and electricity from renewable sources, such as solar or wind energy, with water as the raw material. In this way, electrolysis is particularly resource-saving.

Electrolysis-produced hydrogen is a true all-rounder in industrial processes, transport, and energy sectors, as it is an energy source, a raw material, and an energy storage medium all in one. In its molecular form, it is an energy source, and its potential can be used by converting it into electrons – in other words, it can be used to generate electricity. At the same time, it is gaseous and combustible, so it can be used as an alternative to fossil fuels.

Green hydrogen can be used to decarbonize industries that are unable to dispense with fossil fuels just by switching to electricity. Green hydrogen can also be used in the chemical industry. What’s more, when utilized as a fuel for commercial vehicles and rail vehicles and as a base product for synthetic fuels, hydrogen can play an important role in making the transport sector less dependent on fossil fuels.

Green Hydrogen can be stored, which opens up many possibilities for storing energy in this form on a long-term basis. One particularly promising application is power-to-gas. This involves converting electrical energy into hydrogen and storing it to make it available for a variety of uses. Green hydrogen therefore has the potential to make a key contribution to replacing natural gas, coal, and oil.

Compared to these forms of energy, the crucial difference is that a hydrogen economy is possible without any associated emissions, such as greenhouse gases.

Working principle of the PEM electrolysis stacks

How the Hybrion PEM Electrolysis Stack works

PEM electrolysis involves the use of a proton exchange membrane (PEM) made from a special polymer. This PEM separates the anode and cathode electrically. At the start of the process, liquid, ultrapure water is supplied to the anode side of the electrolyzer. When a voltage is then applied to the two electrodes, protons are released and migrate through the membrane. During this electrochemical process, water is converted into hydrogen and oxygen, with hydrogen forming at the cathode and oxygen at the anode. The advantages of this method include high power density, excellent flexibility, and minimal space requirements.

We manufacture the most important component of a PEM water electrolysis technology – the Hybrion PEM electrolysis stack. This is, in a sense, the beating heart of every electrolysis system, because hydrogen is produced in its cells.

Application areas of Bosch PEM electrolysis stacks

Large-scale industrial hydrogen production for your business

There is a great variety of areas of application, and customer requirements relating to electrolysis technologies are similarly diverse. They range from decentralized hydrogen production to cover industrial companies’ own needs to large-scale systems for energy-intensive industrial sectors or for companies that produce hydrogen on a large scale for export to remote regions.

Bosch PEM electrolysis stacks as a decentralized, flexible container solution
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FAQs about PEM electrolysis and our Hybrion PEM electrolysis stacks

Proton exchange membrane electrolysis (PEM electrolysis) is an electrochemical process for producing hydrogen by means of water electrolysis. The process uses an electrolyzer that contains an anode and a cathode. The anode and cathode are separated electrically by a proton exchange membrane, which is also called a polymer electrolyte membrane. When the electrolysis process runs on electricity from renewable energy sources such as solar power, hydropower, or wind power, the hydrogen produced is known as green hydrogen.

In PEM electrolysis, ultrapure water flows around a proton exchange membrane (PEM). Located between the anode and the cathode, this membrane is ionically conductive. When an electric voltage is applied to both electrodes, the water on the anode side oxidizes to oxygen, free electrons, and hydrogen ions (Oxygen Evolution Reaction, OER). The ions pass through the membrane by diffusion. They then combine with the electrons at the cathode side to form hydrogen gas (Hydrogen Evolution Reaction, HER). The reaction products of PEM electrolysis are hydrogen and oxygen.

A PEM electrolyzer is a system that splits water into its component parts of hydrogen and oxygen by means of an electrochemical reaction. The hydrogen produced in this way is used as an efficient energy source. We manufacture the most important component of a PEM electrolyzer – the stack, which is, in a sense, the beating heart of water electrolysis. There is a great range of areas of application – and the dimensions of electrolysis systems vary greatly, too. They range from decentralized hydrogen production for covering industrial companies’ own needs through to large-scale systems for industrial hydrogen applications or for companies that produce hydrogen on a large scale for export purposes.

A PEM stack is the most important component of a water electrolysis system, which we manufacture in industrialized series production. The stack splits water into oxygen (O₂) and hydrogen (H₂). Our Hybrion stack consists of more than 100 cells and is designed for a power density of 3 A/cm3 and a nominal output of 1.25 MW. This corresponds to a maximum production level of 23 kg of H₂ per hour. Pressures in excess of 30 bar are generated on the hydrogen side. Each Hybrion stack weighs around 2,850 kg and measures 80 × 97 × 150 cm. Depending on the operating point, the stack achieves an efficiency of 80% or more, based on the heating value of H₂.

Compared to other electrolysis methods, such as alkaline electrolysis (AEL), PEM water electrolysis boasts a number of key benefits, including high power density, high energy efficiency, and high hydrogen output pressure. There are other advantages to using PEM electrolyzers, too – they offer maximum flexibility, require very little space, and can be scaled with ease. What’s more, this process is very safe and reliable, making it the ideal technology when combined with renewable energy resources such as wind and solar power.

In PEM electrolysis, ultrapure water flows around a proton exchange membrane (PEM). Located between the anode and the cathode, this membrane is ionically conductive. When an electric voltage is applied to both electrodes, the water on the anode side oxidizes to oxygen, free electrons, and hydrogen ions (Oxygen Evolution Reaction, OER). The ions pass through the membrane by diffusion. They then combine with the electrons at the cathode side to form hydrogen gas (Hydrogen Evolution Reaction, HER). The reaction products of PEM electrolysis are hydrogen and oxygen.

The comissioning of Bosch Hybrion PEM electrolysis stacks for customers starts in 2025. All technical specifications given are development objectives and refer to the beginning of life.

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