What is PEM electrolyzer?
PEM (proton exchange membrane) electrolyzer is a device that uses electricity as energy and uses proton exchange membrane technology to electrolyze water to produce hydrogen. It is particularly suitable for green hydrogen production technology coupled with renewable electricity.
| Contents What is a PEM electrolyzer? I. Technical Principles 1. Anode Reaction (Oxygen Evolution) 2. Proton Conduction 3. Cathode Reaction (Hydrogen Evolution) II. Core Components III. Advantages of PEM 1. High Current Density 2. High Purity of Hydrogen 3. Fast Response 4. High Output Pressure 5. Compact Structure, Small Size, and Safe IV. Applications 1. Industry 2. Transportation 3. Grid Regulation V. Technical Comparison Summary |
I. Technical Principle
The PEM electrolyzer uses pure water as raw material and decomposes it into hydrogen and oxygen through electrochemical reactions.
1. Anode reaction (oxygen evolution)
Reaction formula: 2H₂O→O₂+4H⁺+4e⁻
Water molecules are decomposed into protons (H⁺), electrons, and oxygen under the action of the anode catalyst.
2. Proton conduction
H⁺passes through the proton exchange membrane PEM to the cathode. The PEM membrane is composed of materials such as perfluorosulfonic acid resin, which allows protons to pass through while blocking gas crossover.
3. Cathode reaction (hydrogen evolution)
Reaction formula: 4H⁺+4e⁻→2H₂
The protons combine with the electrons at the cathode to generate hydrogen gas.
II. Core Components
The core structure of the PEM electrolyzer includes the following parts:
| Parts Name | Effection | Material |
|---|---|---|
| Membrane Electrode Assembly (MEA) | The core area where the reaction occurs, including the proton exchange membrane and the cathode and anode catalyst layers | Anode: Strong acid corrosion resistant, mainly iridium, ruthenium precious metal catalysts Cathode:platinum catalyst |
| Gas diffusion layer | Promote gas transport and support catalyst | High conductivity and corrosion resistance are required, titanium sintered felt is commonly used |
| Bipolar plate | Divide single cells, conduct current, and distribute gas and liquid channels | The surface of titanium plate needs to be plated with gold and niobium for corrosion protection |
| Proton Exchange Membrane | Conducting protons, isolating gases | Dense ion-selective perfluorosulfonic acid proton exchange membrane |
III. Advantages of PEM
1. High current density
The current density can reach 1.2-2.2A/cm², while the alkaline electrolyzer is 0.2-0.4A/cm². The hydrogen production efficiency per unit area is higher.
2. High hydrogen purity
The purity of the product hydrogen is as high as 99.999%. The next process is just a simple dehydration treatment. No additional work is required.
3. Fast response
The startup time is speedy, only a few seconds, which perfectly matches the fluctuating and unstable energy of wind power and photovoltaic power.
4. High output pressure
The output pressure of hydrogen reaches 3.5-3.MPa. It doesn’t need additional compression and can be directly connected to the hydrogen storage bottle.
5. Compact structure, small size, and safety
The zero-distance structure between components reduces the internal resistance. The volume is 30% smaller than that of the alkaline electrolyzer, and there is no alkali corrosion.
IV. Applications
1. Industry: used in carbon-intensive industries such as petroleum refining, chemical synthesis of ammonia, and steel
2. Transportation: Hydrogen is produced on-site at hydrogen stations without the need for long-distance transportation
3. Grid regulation: cooperate with wind power and photovoltaic power to achieve “electricity-hydrogen-electricity” or “electricity-hydrogen” to reduce the pressure on the grid.
V. Technical Comparison
| Item | PEM electrolyzer | Alkaline electrolyzer |
|---|---|---|
| Current density | High（>2A/cm²） | Low（0.2–0.4A/cm²） |
| Response speed | Fast, calculate according to second | Slow, Fast, calculate according to minute |
| Gas pressure | Hydrogen high pressure, direct output | Product needs to be compressed |
| Detailed application scenario | Carry fluctuating power grid | Must have stable power supply |
Summary
PEM electrolyzer has the characteristics of being highly flexible, adaptable to green electricity, and zero carbon emissions. And it has become the core technology of green hydrogen. However, the cost constraints limit the large-scale application of PEM. In the future, we need to innovate materials, upgrade processes, and explore hybrid technologies such as AEM to promote the development of green hydrogen.
