Catalysis is the increase of the rate of a chemical reaction by lowing the necessary energy. It is done by using a substance, known as a catalyst, that is not consumed during the reaction. In some cases, the goal of catalysis is to produce a specific desired reaction. Life is only possible thanks to the catalysis of biochemical reactions by enzymes.

In the H2GREEN system, the catalysts are enzymes (active proteins). They facilitate reactions by reducing the energy required, which increases the speed and energy efficiency.

The term “catalysis” designates a process which aims to modify the chemical kinetics by lowering the energy barrier to be crossed. The goal of catalysis is to increase the rate at which a chemical reaction occurs or, sometimes, to favour one reaction over another.



A catalyst is a substance that decreases the activation energy and increases the rate of a chemical reaction without being consumed in that reaction.

Energy Vector

An energy vector conveys energy from a source (eg the sun) to its use (eg motor).


Enzymes are proteins that act as biological catalysts, which means that they speed up the body's biochemical reactions and make life possible. They are naturally present in vegetables and animals. They can also be produced industrially by fermentation.


Enzyme with simplified structure keeping the active site.

Native enzyme

Enzyme with the same structure as in Nature.

HY (Hydrogenase)

Enzyme capable of reducing proton (EZY) or oxidising H2 (E-FCH).

PSII (Photosystem II)

Photoenzyme capable to oxidise water with light (water photo-splitting).


“Electrolysis, process by which electric current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction). The process is carried out in an electrolytic cell, an apparatus consisting of positive and negative electrodes held apart and dipped into a solution containing positively and negatively charged ions.” [Source: Brittanica online encyclopaedia]

Photoenzymatic electrolysis

Electrolysis using photosynthetic enzymes that catalyse a photochemical reaction – in this case, the conversion of light into electricity to split water into hydrogen and oxygen. Using enzymes to replace platinum is a cost-effective alternative to reduce costs and improve profits in the production of hydrogen, while using only 100% renewable resources. See also: Algae & enzymes Q&A.

Enzymolysis (EZY)

Electrically powered PEM electrolysis with enzymatic catalytic system producing H2 from water.

ALK ELY (Alkaline Electrolysers)

System producing H2 from water with electricity in NaOH (alkaline) medium.

PEM ELY (Proton Exchange Membrane Electrolyser)

System producing H2 from water with electricity using Platinum as catalysers in acid medium (best performance on the market).

ENZYMEA (Enzymatic MEA)

Enzymatic Membrane Electrode Assembly in PEM ELY & FCH.

Fuel cell (FCH)

A fuel cell is system producing electricity by oxidising H2 using Platinum as a catalyst.

Enzymatic fuel cell (Enzy-FCH)

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidising agent (often oxygen) into electricity. Today, fuel cells use precious metals (platinum) as a catalyst. An enzymatic fuel cell (also called an enzymatic biofuel cell) is a specific type of fuel cell that uses enzymes as a catalyst to oxidise its fuel, rather than precious metals.

Electrodes, cathode and anode

The anode is the electrode where the process of oxidation occurs. In other words, it is where the  electrons from the substrate’s molecules are taken.  In the case of the H2GREEN enzymolyser, photoenzymes take electrons from water using sunlight energy.

In the case of our enzymatic fuel cell, the enzymatic anode takes electrons from H2 to produce electricity.

The cathode is an electrode where the process of reduction occurs. In other words, it is where a molecule receives electrons.

In the case of the H2GREEN enzymolyser, enzymes give electrons (taken from water and coming from the anode) to the protons producing H2 at the cathode.


Photosynthesis is the chemical process whereby green plants (and most algae) convert sunlight into sugar, which is then stored in the plant. Then these sugars lead to the rest of the components.

Essentially, light energy (from the sun) is converted to chemical energy (in the plant).

When sunlight reaches the leaves of a plant is sets off the process of photosynthesis.

  • A molecule of chlorophyll (the compound that gives plants a green colour) absorbs the light.
  • A sequence of chemical reactions transfers the light energy (from the sun) into chemical bonds that hold molecules together. These molecules store the energy from the sunlight as chemical energy.
  • The plant uses this stored chemical energy along with water and carbon dioxide (from the air) to produce glucose* and oxygen. The plant then uses the glucose to make compounds of cellulose and starch, which store energy. The oxygen is released into the air.

The photosynthesis formula is: 6 CO2 + 6 H2O -> CH12 O6 + 6 O2.

This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll into a glucose* molecule and six oxygen molecules.

*glucose (CH12 O6) is a type of carbohydrate, or sugar, composed of carbon, hydrogen and oxygen.

As the plant binds molecules into larger and larger chains, it captures and stores energy in the bonds, to be released later. The plant uses the largest molecules to construct cell walls as the plant grows larger. If we – or other animals – eat the plant, we absorb its stored energy to use as fuel in our body.


Hydrogen Generation by REnewable Energy Solar powered

H2GREEN system

Coupling of photoenzymatic H2 generation and enzymatic Fuel Cell


Public Interest Scientific Foundation promoting H2 economy & renewable solutions (since 2011)


Hydrogen Worldwide Integration, a private company founded in 2013

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