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Application of PPS diaphragm in alkaline water electrolysis hydrogen production diaphragm
Release time:
2024-12-20
As a secondary energy source with abundant sources, green and low carbon, and wide applications, hydrogen energy is of great significance to building a clean, low-carbon, safe and efficient energy system and achieving the goals of carbon peak and carbon neutrality. Water electrolysis technology is considered to be the most ideal and environmentally friendly way to produce hydrogen. Among them, alkaline water electrolysis hydrogen production technology occupies a dominant position in water electrolysis hydrogen production due to its advantages such as low cost, long life and abundant material sources.
The alkaline water electrolysis hydrogen production system mainly includes the alkaline hydrogen production electrolyzer body and the BOP auxiliary system. The alkaline hydrogen production electrolyzer body is assembled from end pressure plates, sealing gaskets, plates, electrodes, diaphragms and other components. Among them, the material selection and structural design of the diaphragm are crucial to improving the efficiency and stability of the entire system. During the electrolysis process of the alkaline electrolyzer, the anode produces oxygen and the cathode produces hydrogen. The main function of the diaphragm is to prevent the mixing of hydrogen and oxygen and provide good ion conductivity.
Alkaline hydrogen production diaphragms have gone through three generations of development. The first generation was the asbestos diaphragm, which has now been eliminated; the second generation was the PPS (polyphenylene sulfide) diaphragm, which is the current mainstream application; the third generation is the composite diaphragm, which is regarded as the future trend.
(Ⅰ) PPS diaphragm
PPS is the most commonly used organic fiber material for alkaline water electrolyzer diaphragms. It is a linear crystalline thermoplastic resin with a phenylthio group in the main chain of the molecule, which is made from p-dichlorobenzene and NaS as raw materials and N-methylpyrrolidone as solvent through a condensation reaction at 135-350°C.
The advantages of PPS diaphragm lie in its excellent electrical properties and chemical stability. It has high ion selectivity and can effectively promote the migration of ions, thereby improving the electrolysis efficiency. At the same time, PPS diaphragm also has good alkali resistance and high temperature resistance, and can adapt to the harsh environment in the process of alkaline water electrolysis to produce hydrogen.
(II) Composite diaphragm
Since the PPS diaphragm will shrink, harden and become brittle due to heat during the service of the alkaline aqueous solution electrolyzer, the diaphragm resistance will increase, the working efficiency will be low and the energy consumption will be high. Therefore, domestic and foreign companies have successively developed composite diaphragms with excellent performance, using PPS diaphragms as the substrate and coated with inorganic substances on the surface. The main purpose of the surface coating of the composite diaphragm is to ensure the mechanical properties of the diaphragm, improve the hydrophilicity of the diaphragm, improve the compatibility of the diaphragm with the electrolyte, and reduce the internal resistance of the electrolyzer.
At present, PPS diaphragms are the mainstream in the industry, accounting for more than 95% of shipments. Domestic composite diaphragms are in the stage of moving from research and development to production and sending samples to downstream customers.The price of composite diaphragms is more than twice that of PPS diaphragms, and the high price restricts the promotion of composite diaphragms.
Whether it is a traditional PPS diaphragm or a composite diaphragm, there is room for further optimization of its performance and price. We believe that through the iteration of new diaphragm technologies, the research and development of process equipment, and the realization of large-scale production, the technological breakthrough of diaphragms will continue to help reduce costs and increase efficiency in alkaline water electrolysis hydrogen production.
PPS diagram,ALK hydrogen electrolyzer,alkaline electrolyzer
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