Water electrolysis

PEM-Electrolysis

In scope to the Power-To-Gas concepts, the production of Hydrogen via PEM-Electrolysis is one of the key technologies for energy recovery of the future. This process is, so to speak, the reversal of a fuel cell technology. The water electrolysis is based on the decomposition of water into its elements H2 und O2 trough electrochemistry reactions which are initialized by applying an electric potential. The proton-conductive membrane is thereby as high-functional separator the crucial core component. Due to the functional chemical side groups within the polymer matrix the protons were transferred from the anode through the membrane to the cathode. There the protons recombine with the electron, which comes over an electrical conductor also to the cathode, to the high purity hydrogen. At the same time, the generated oxygen on the anode side is separated and can also be stored in a very pure form or used directly.

Anode reaction           H2O → 2 H+ + 0,5 O2 + 2 e-

Cathode reaction       2 H+ + 2 e- → H2

In the overall balance one molecule H2 and a half molecule O2 are formed during the decomposition of water per water molecule.


By PEM water electrolysis high current densities can be achieved, this is based among other things on the high proton conductivity of coming to use membranes. In this application segment FUMATECH BWT GmbH offers different fabric-reinforced membranes. They are characterized by an excellent proton conductivity and low cross-over of the reactants. In addition, they show a high chemical and mechanical resistance. In particular, the fabric-reinforcement use of membranes under elevated operating pressure is possible. The high stability of the membranes supports the longevity of the entire electrolysis system.

 

Alkaline-Electrolysis

The alkaline electrolysis is already an industrially established process. The hydrogen produced by this method is characterized by its high purity and is also used for this reason mainly in chemical process technology. But just for the future energy industry, this method for producing hydrogen is an attractive additional tool. The application of a functional membrane for highly efficient transferring of OH - -ions undergoes in this application, a steady increase in recent years demand. The demands to the used membrane materials concerning chemical stability are very high. In operation will be KOH solution up to 40 %-wt. The operating temperature of the industrial plants is partly above 80 ° C and it is planned to rise up the operating pressures up to 30 bar in the future.

In the alkaline water electrolysis cell, the water will be separated at the cathode to H2 and OH- - ions.
The electrochemical processes in the cell are seen as follows:

Cathode reaction       2 H2O + 2 e- → H2 + 2 OH-

Anode reaction           2 OH- → 0,5 O2 + H2O + 2 e-

In the overall balance therefore one molecule of hydrogen and one oxygen particle were recovered from one molecule of water.

FUMATECH BWT GmbH offers both, plain films and fabric-reinforced membranes with high conductivity and low H2 cross-over for the use in the alkaline electrolysis field. Especially the reduced hydrogen permeability is an important advantage in the efficiency recovery of the entire electrolysis system represents.

 

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