Intelligent Solutions for Hydrogen Production from Water Electrolysis

Process Introduction

Hydrogen production by water electrolysis is a process that generates hydrogen gas (H2) and oxygen gas (O2) through the electrolysis of water (H2O). Its basic principle is to use electrical energy to decompose water into hydrogen and oxygen, and the reaction formula is: 2H2O→2H2+ O2. This process usually takes place in an electrolytic cell, which is equipped with an anode and a cathode, separated by an electrolyte. Commonly used electrolytes include alkaline solutions (such as potassium hydroxide), proton exchange membranes (PEM), or solid oxides (SOEC).

In an alkaline electrolytic cell, water gains electrons at the cathode to produce hydrogen gas and hydroxide ions. The hydroxide ions migrate through the electrolyte to the anode, where they lose electrons to form oxygen gas and water. PEM electrolytic cells use a proton exchange membrane as the electrolyte. Water is decomposed into oxygen, protons, and electrons at the anode. The protons pass through the membrane to reach the cathode, where they combine with electrons to form hydrogen gas. SOEC electrolytic cells operate at high temperatures and use solid oxide electrolytes to conduct oxygen ions. They have relatively high efficiency but require a high-temperature environment.
The key advantage of hydrogen production by water electrolysis is that its product is high-purity hydrogen gas, and the process is pollution-free. It is especially suitable for green hydrogen production driven by renewable energy electricity. However, it has relatively high energy consumption, and the cost is greatly affected by the electricity price. With the advancement of technology and the development of renewable energy sources, hydrogen production by water electrolysis is expected to become an important part of the future clean energy system.

Technical Features

1. In terms of the purity of the produced hydrogen gas, it can reach 99.99%, and it can be directly used in other fields without additional purification operations.

2. In terms of environmental protection, since this process uses water as the raw material to produce oxygen and hydrogen, there is no emission of other pollutants, which provides a high level of environmental protection.

3. This process has diverse applicable scenarios. It can be used not only for small-scale experimental hydrogen production but also for large-scale centralized hydrogen production.
4. This process can be started and stopped rapidly, and it is flexible and controllable.

5. The process has diversified technical routes, including Alkaline Electrolyzer (AEL), Proton Exchange Membrane Electrolyzer (PEMEL), and Solid Oxide Electrolyzer (SOEL). Each technical route has its own characteristics. AEL has a low cost and mature technology; PEMEL has relatively high efficiency; SOEL has a compact structure and a higher current density, but it has a high cost and is still in the research and development stage.

6. Hydrogen production by water electrolysis can absorb excess renewable electric power energy, achieving green hydrogen production and energy transformation.

Hydrogen Production Process by Water Electrolysis

01 Pretreatment of Raw Water

The raw water is first filtered to remove suspended solids and particles. Then, it undergoes ion-exchange processes through cation-exchange resins and anion-exchange resins respectively. Subsequently, high-pressure is applied to force the water through a semi-permeable membrane for reverse osmosis. By combining ion-exchange and electrodialysis for continuous deionization, high-purity deionized water can be obtained.
02 Reaction in the Electrolytic Cell

The electrolytic cell consists of a cathode, an anode, and a diaphragm. Direct current is passed through the cathode and the anode respectively. The diaphragm is used to separate hydrogen and oxygen while allowing ions to pass through.
Cathode reaction: 2H2O+2e−→H2↑+2OH−. Water molecules gain electrons at the cathode to produce hydrogen gas and hydroxide ions.
Anode reaction: 4OH−→O2↑+2H2O+4e−. Hydroxide ions lose electrons at the anode to produce oxygen gas and water.
Hydroxide ions (OH−) migrate between the cathode and the anode through the electrolyte (such as KOH solution) to complete the charge transfer.
03 Gas Separation and Collection

The hydrogen gas produced at the cathode is mixed with the electrolyte. The hydrogen gas is separated by a gas-liquid separator, and the remaining electrolyte is returned to the electrolytic cell for recycling.
The oxygen gas produced at the anode is also separated by a gas-liquid separator. The oxygen gas can be collected for utilization or discharged.
The separated hydrogen gas may contain trace amounts of moisture and impurities. It needs to be further purified through a drying tower and an adsorption tower to ensure that the purity of the hydrogen gas reaches over 99.99%.
04 Post-treatment of Hydrogen Gas

The hydrogen gas is compressed to a pressure of 20-30 MPa by a compressor and stored in a high-pressure hydrogen storage tank. If liquid hydrogen is required, the hydrogen gas is cooled and liquefied for low-temperature storage.

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