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Hydrogen is not only a key raw material for the chemical industry, but also a carbon-free fuel for industry and transportation
.
However, the cost of green hydrogen production remains high compared to the carbon-based energy (such as methane) steam reforming process used in most industrial hydrogen production
.
The ion exchange membrane is the core component of the electrolysis cell and is critical to the electrolysis efficiency and electrolysis reliability
.
"With this innovative membrane technology, we hope to commercialize green hydrogen production, making it economical and efficient
," said Oliver Conradi, responsible for membrane technology innovation, Creavis, Evonik's strategic innovation division
.
The membrane technology developed by Evonik is expected to reduce the cost of hydrogen production from water electrolysis
.
Disadvantages of the prior art
Disadvantages of the prior artAlkaline water electrolysis (AEL) is one of the most widely used processes in existence
.
To ensure separation of the reaction products and avoid their recombination causing an explosion, a membrane is required between the anode and cathode of the electrolytic cell
.
To allow the gas to pass through, the AEL uses a membrane with a porous structure, thus limiting the operation of the device under pressurized conditions
.
Another technology is proton exchange membrane (PEM) electrolysis to produce hydrogen
.
In this technology, the proton exchange membrane is not only used to separate the reaction products, but also allows for a more compact design of the electrolytic cell, since it is composed of a conductive polymer, while the electrodes are located on both sides of the membrane, and the water to be electrolyzed flows through the anode, producing The hydrogen ions pass through the proton exchange membrane from the anode side to the cathode, and generate hydrogen molecules after the cathode reaction
.
Compared to AEL systems, PEM electrolyzers can not only withstand higher current densities, but also cope with larger load fluctuations
.
Since the technology can be implemented under pressure, the subsequent hydrogen compression also consumes less energy
.
Although the PEM system has certain advantages in technology, the investment cost is extremely high
.
"PEM reacts under acidic conditions, and the material of the electrolysis system must have excellent corrosion resistance and require catalysts made of precious metals such as platinum and iridium; and the electrolysis cell must be made of titanium or even platinum titanium,
" Conradi explained
.
Evonik anion exchange membranes: combining the advantages of existing technologies
Evonik anion exchange membranes: combining the advantages of existing technologiesCompared to AEL or PEM processes, Evonik's anion exchange membrane (AEM) electrolysis combines the advantages of both
.
The structure of an AEM cell is similar to that of a PEM: a membrane made of ion-conducting plastic, also known as an ionomer, separates the electrodes on either side of the membrane
.
The electrodes are also made from ionomers and incorporate catalyst particles
.
"
Unlike PEM, AEM's electrolyzers can rely on non-precious metal catalysts such as nickel-based catalysts, thereby effectively reducing material costs
.
Conradi said
.
Like the AEL process, the AEM reaction will take place in an alkaline environment
.
The water is electrolyzed at the cathode and hydrogen is
produced.
Other features of the AEM electrolysis technology include high current density, high efficiency and flexibility.
.
Despite initial progress in research and development, the lab's focus remains on optimizing the membrane formulation
.
“An important factor that affects its efficiency is the contact resistance between the membrane and the electrode
.
To keep the resistance as low as possible, we need a good ionic connection between the membrane and the electrode
.
So, we need not only continue to optimize the polymer of the membrane formulation, and custom development of an electrode binder for the membrane,
” Conradi said
.
In addition, the team is further optimizing the coating and other processes to achieve mass production of membrane materials
.
Evonik's goal is to develop a complete electrolysis system to enable large-scale hydrogen production from renewable energies
.
To this end, the company is actively cooperating with other partners
.
In this research project, called CHANNEL, companies and research institutes including electrolyzer developer Enapter, energy company Shell, Germany's Jülich Research Center, and Norwegian Institute of Technology and Industry will design, based on Evonik's membrane technology, , Build and test the AEM electrolysis system
.
The related technology verification model is expected to be launched in 2022
.
In China, the technology has also attracted a lot of interest
.
At present, Evonik is actively seeking local partners to promote the relevant research process
.
