Hydrogen is considered a key technology for the energy transition and plays a central role in the decarbonization of industry, mobility and energy supply. But how is hydrogen actually produced? In this article, we will introduce you to the three most important processes: Electrolysis, steam reforming and pyrolysis.
Electrolysis – hydrogen from electricity and water
Electrolysis is a climate-friendly process for producing hydrogen. Water (H₂O) is broken down into its components hydrogen (H₂) and oxygen (O₂) using electrical energy. The process takes place in an electrolyser in which two electrodes – anode and cathode – are separated by a conductive liquid (electrolyte).
Depending on the type of electrolyzer, a distinction is made between different technologies, including:
– Alkaline electrolysis (AEL)
– Proton exchange membrane electrolysis (PEM)
– High-temperature electrolysis (SOEC)
Electrolysis is particularly sustainable if the electricity required comes from renewable sources such as wind or solar energy. In this case, we speak of green hydrogen, which is produced almost CO₂-free.
Steam reforming – hydrogen from natural gas
Steam methane reforming (SMR) is currently the most commonly used process for hydrogen production worldwide. In this process, natural gas (mainly methane) is converted into hydrogen and carbon monoxide with steam under high pressure and at temperatures of around 800-900 °C in a reactor.
In a second step, the so-called water-gas shift reaction, the resulting carbon monoxide is converted with further water vapor to carbon dioxide (CO₂) and additional hydrogen.
One disadvantage of this process is the high CO₂ emissions – around 9 to 10 tons of CO₂ per ton of hydrogen. However, if the resulting CO₂ is captured and stored (carbon capture and storage, CCS), it is referred to as blue hydrogen.
Pyrolysis – hydrogen from methane without CO₂
Methane pyrolysis is an innovative process in which methane is thermally split into hydrogen and solid carbon – without producing any CO₂:
This process takes place at temperatures of around 1000 °C, usually in a special reactor environment, e.g. a plasma reactor. The big advantage: no gaseous CO₂ is produced, but solid carbon, which can be used as a building material or in industry, for example.
Hydrogen from pyrolysis is also known as turquoise hydrogen. The technology is still largely in the development stage, but offers great potential for a low-carbon hydrogen economy.
Conclusion
Hydrogen can be produced in different ways – from climate-friendly electrolysis to steam reforming, which dominates today, to the promising pyrolysis process.
