Alphabet Glossary Filter

Alkaline water electrolysis

Alkaline water electrolysis (AWE) is the process used to produce hydrogen from water using electricity. When electricity from renewable energy sources is used, it is referred to as green hydrogen.

Ammonia (green)

Green ammonia is produced using electricity from wind, solar, or hydropower as part of the water electrolysis process. The resulting hydrogen is then catalytically reacted with atmospheric nitrogen to form ammonia. Ammonia is a chemical compound with significant technical importance for the production of nitrogen fertilizers, purification of exhaust gas in power plants, and as a refrigerant.


Abbreviation for alkaline water electrolysis.


Product name of the electrolysis technology marketed by thyssenkrupp nucera in the form of a filter press.

Blue hydrogen

Hydrogen generated from natural gas (steam reduction), in which the resulting CO2 is not emitted into the atmosphere, but instead, stored or further processed industrially (Carbon Capture & Storage [CCS]).


Bipolar membrane is the product name of the single-element electrolysis technology marketed by thyssenkrupp nucera.


Abbreviation for chlorine-alkaline electrolysis.

Chlor-alkali electrolysis

Process for producing the important basic chemicals chlorine, hydrogen, and sodium hydroxide (caustic) soda from sodium chloride and water.

CO2 emissions

Emissions of the molecule carbon dioxide, which consists of carbon and oxygen. Emissions are considered one of the driving forces of global warming.


Decarbonization involves the complete elimination of carbon in the form of carbon dioxide. Complete decarbonization of the industry is not possible, because carbon in bound form is an important element for many basic chemical products, such as methanol.


Defossilization involves replacing fossil fuels such as oil and natural gas with renewable energy sources such as green hydrogen and avoiding carbon dioxide emissions (defossilized).

Diaphragm method

One of the three most important chlor-alkali-electrolysis processes. This process prevents the mixing of reaction products in the electrolysis cell using a porous diaphragm.


Synthetic liquid or gaseous fuels produced from green hydrogen and carbon dioxide.


A process in which a chemical compound is split using electricity. In water electrolysis, water is split into its elementary components – hydrogen (H2) and oxygen (O) – in an electrolysis cell using electrical energy.


An electrolyzer consists of several electrolysis cells arranged in a series, within which a redox reaction is forced by the addition of electrical energy, for example, to split water into the elementary components of hydrogen and oxygen.


(environment, social, governance)

An internationally established approach at companies and in the financial world to show whether and how environmental aspects, social aspects, and type of corporate governance are taken into account or evaluated in corporate decisions and corporate practice, including in company analyses by financial service providers.

Green hydrogen

Hydrogen, in which the electricity required to split water into hydrogen and oxygen comes from alternative energy sources (e.g., solar energy, wind, or hydropower).

Grey hydrogen

Hydrogen generated from fossil fuels (natural gas, oil, coal). Currently, the most common process is the generation from natural gas through the process of steam reforming. The production of one ton of hydrogen releases around ten tons of carbon dioxide.


The flagship project for the series production of electrolyzers for the production of hydrogen.


Abbreviation for hydrochloric acid.

HCI-ODC electrolysis

The process of HCl membrane electrolysis with oxygen depolarized cathodes (HCl-oxygen depolarized cathodes).

HCl electrolysis

HCl electrolysis is a process for converting hydrochloric acid into chlorine and hydrogen.

High-temperature electrolysis (HTEL)

A form of water electrolysis in which processes are carried out at very high temperatures (up to 900 degrees Celsius), which increases efficiency and, consequently, reduces the power requirement.


The element with atomic number 1 and the earliest and most common atom in the universe. The combustible gas can serve as an energy carrier that does not release any environmentally or climate-damaging substances (especially CO2) during combustion. The degree of climate neutrality differs, depending on the production method used.

Membrane process

One of the three most important chlor-alkali-electrolysis processes. A plastic membrane cell prevents the reaction products from mixing in the electrolysis cell.


A chemical reaction in which methane is produced from hydrogen and carbon dioxide (CO2). The CO2 can come from the air or originate from biogas or industrial plants. When green hydrogen is used, methane is available after this process as a regeneratively produced synthetic gas.


Abbreviation for oxygen depolarized cathodes.

ODC process

In chlorine electrolysis with oxygen depolarized cathode, the same electrolysis cell is used as in the membrane process, but the conventional cathode is replaced by a cathode with a special oxygen diffusion surface. Oxygen is introduced behind this and is reduced together with water to hydroxide ions.

PEM electrolysis

Proton exchange membrane (PEM) electrolysis is a water electrolysis process. In contrast to alkaline electrolysis, it is carried out in an acidic medium.

Pink hydrogen

Climate-neutral hydrogen generated by electrolysis using electricity from nuclear power.


Processes that convert electricity into other energy carriers (usually into chemical energy carriers) that can be used for electricity storage, as fuels, or as raw materials for the chemical industry. Depending on the intended use and the form of energy produced, other references include power-to-fuel, power-to-chemicals, power-to-gas or power-to-heat.

Renewable energy

Renewable energies are energies from the sun, wind, water, and geothermal resources.

Reverse power generation

The further processing of artificially produced hydrogen with CO2 into methane and use via the gas grid. If required, the gas can also be converted back into electricity in gas and steam power plants (“reverse power generation”).

SDG (Sustainable Development Goals)

The 17 goals agreed by the UN member states to ensure sustainable development at the economic, social, and environmental levels.

Steam reforming

Process for generating hydrogen from fossil, carbon-containing fuels such as natural gas, coal, and oil. Because of the release of the waste product CO2 into the atmosphere, gray hydrogen is not climate-neutral.

Turquoise hydrogen

Turquoise hydrogen is produced when methane in natural gas is split by pyrolysis into hydrogen and solid carbon, which can be stored or reused but not avoided. The production of turquoise hydrogen is climate-neutral when energy from renewable sources is used in the process.

UN Global Compact

Worldwide UN initiative to shape globalization in social and environmental terms, with the aim of raising awareness and encouraging companies to act in order to achieve the Sustainable Development Goals (SDGs) by 2030.

Water electrolysis

The splitting of water in an electrolyzer with the aid of electricity into the elements of hydrogen and oxygen.

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