Four technical routes for producing hydrogen by water electrolysis
Green hydrogen is produced by electrolyzing water. Currently, there are four main technical routes on the market: alkaline electrolysis (ALK), proton exchange membrane electrolysis (PEM), solid oxide electrolysis (SOEC) and anion exchange membrane (AEM).
Alkaline electrolysis (ALK) technology is the most mature technology in the field of water electrolysis. The basic principle is that water is decomposed into hydrogen and oxygen through electrochemical reactions under the action of electric current, and the two are precipitated at the cathode and anode of the electrolytic cell respectively.
The working principle of PEM electrolysis is that water is decomposed into oxygen and hydrogen ions (H+) through catalysis at the anode. The hydrogen ions then pass through the electrolyte diaphragm to the cathode and obtain electrons at the cathode to generate hydrogen. After the reaction is completed, hydrogen and oxygen are collected and transported through the bipolar plates of the anode and cathode respectively; this technology is currently in the early stage of marketization. The core components include polymer films with excellent proton exchange capacity and anode and cathode catalyst layers that are tightly attached to both sides of the electrolyte film.
As a new type of electrolysis equipment, the AEM electrolyzer uses a cation exchange membrane as a diaphragm and can operate in a wider pH range.
The SOEC electrolyzer is a high-temperature electrolysis device. Its hydrogen production principle is to use solid oxides as electrolytes and operate under high temperature conditions to achieve electrochemical decomposition of water or carbon dioxide.