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How exactly does the production hydrogen work?

Green hydrogen is to enable energy-intensive sectors such as the steel and chemical industries to reach climate neutrality. But where exactly does the colourless gas come from?

^{This is what it’s all about: green hydrogen has the potential to not only revolutionise the economy, but also be a gamechanger for the energy transition.}

Depending on the method of production and the primary energy source for it, hydrogen is assigned a ‘colour’. A key method is electrolysis: this involves using an electric current to split water into hydrogen and oxygen and takes place in an electrolyser.

Electrolysers are essential for the energy transition as they convert excess electricity from renewables into hydrogen and store it. When needed, the hydrogen can be reconverted into power – this is a key enabling technology for sector coupling, especially at times when there is little wind and solar energy to be harnessed.

^{Only green hydrogen is truly sustainable}

Green hydrogen is produced through electrolysis using electricity from renewables such as wind or solar energy. It is free from CO₂ emissions. It can be used to render industrial processes and mobility more climate-friendly and is the most sustainable option in the long term.

Blue hydrogen, which is derived from natural gas, can help reduce CO₂ emissions in the short term. Almost all of the CO₂ generated in the process can be captured and stored below the ground (CCS), which makes it a low-CO₂ option.

Grey hydrogen currently dominates global production. In Germany, it is mainly used by the chemical industry. It is obtained from fossil fuels such as natural gas in a process called steam reforming. The CO₂ generated by this method is not stored, but released into the atmosphere, where it acts as a greenhouse gas.

Turquoise hydrogen is produced through methane pyrolysis, a thermal process used to split methane. This produces solid carbon rather than CO₂, eliminating the need to store gaseous CO₂.

^{What does the inside of an electrolyser look like?}

An electrolyser cell is made of two electrodes separated by an electrolyte and a separator. The electrodes are used to induce a chemical process that splits water into hydrogen and oxygen. The electrolyte’s job is to enable the transfer of energy, whilst catalysts improve efficiency rates.

Industrial-type electrolysers are composed of stacks of many cells and come with additional components such as transformers, pumps, purification and cooling systems and safety technology.

At present, there are four technologies in the spotlight: the mature procedures of alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEM), and those of anion-exchange membrane electrolysis (AEM) and solid oxide electrolysis (SEOC).

The roadmap for the emergence of a hydrogen economy – the National Hydrogen Strategy – , information on funding possibilities, and the Hydrogen Import Strategy can be found in the ministry’s dossier on hydrogen.