Pros and Cons of Common Diaphragm Materials for Alkaline Electrolyzers

In alkaline hydrogen production electrolyzers, the membrane is the core component second only to the electrodes, serving two main functions: first, to strictly block hydrogen and oxygen gases, eliminating the risk of mixing and explosion; and second, to act as a hydroxyl ion conduction channel, ensuring efficient operation of the electrolysis reaction. From early highly toxic and carcinogenic asbestos membranes to today's mainstream PPS fabric membranes, and then to porous composite membranes, the technological iteration of alkaline hydrogen production membranes has consistently focused on four core objectives: low resistance, high stability, long lifespan, and low cost.

A qualified membrane must simultaneously meet four core indicators: ion conductivity, gas barrier properties, chemical stability, and mechanical strength. These indicators are interdependent: increasing porosity reduces resistance but exacerbates gas leakage; enhancing density reduces gas leakage but increases ion transport impedance. Technological breakthroughs in various membrane types essentially involve optimizing and balancing this contradiction.

I. Detailed Comparative Analysis of Mainstream Alkaline Electrolyte Diaphragm Materials

1. Asbestos Diaphragm: An obsolete first-generation material, banned globally.

Asbestos diaphragms were the first-generation product for alkaline hydrogen production, dominating the market in the 20th century. Due to their strong carcinogenicity, they have been banned globally.

Material and Structure: Wet-formed natural serpentine asbestos fibers, porous mesh structure, fiber diameter 0.1–5μm, porosity 60%–80%.

Core Advantages: High hydroxyl content on fiber surface, strong hydrophilicity, rapid electrolyte wetting; alkaline and high temperature resistance, stable operation at 30% KOH and 90℃; extremely low raw material cost, simple preparation process.

Core Disadvantages: Highly toxic and carcinogenic, listed as a hazardous chemical in many countries; loose pores, poor gas barrier properties, high cross-contamination rate; fibers easily swell with long-term use, surface resistivity 0.5–0.8 Ω・cm², energy consumption 20%–40% higher than modern diaphragms; poor mechanical strength, easily damaged, lifespan only a few thousand hours.

2. PPS Fabric Separator: The Preferred Material for Current Industrial Production

Polyphenylene sulfide (PPS) fabric separators are an ideal alternative to asbestos separators. Their high stability and cost-effectiveness have made them the preferred material for current alkaline hydrogen production industrial projects.

Material and Structure: Made from PPS filaments/short fibers, these separators are woven, hydroentangled, and hot-pressed to create a three-dimensional dense fabric structure. Some products undergo plasma treatment and coating for hydrophilic modification.

Core Advantages: Stable molecular structure, resistant to acids, alkalis, high temperatures, and oxidative hydrolysis; can operate continuously at 30% KOH and 180℃; tensile strength 30–35 MPa, strong impact resistance, and a lifespan of 5–10 years; high domestic raw material availability and mature technology; cost per ton of membrane is only 60%–70% of that of composite separators, making it suitable for large-scale mass production.

Core Disadvantages: The molecule lacks polar groups, resulting in poor natural hydrophilicity and difficulty in electrolyte wetting; the pore size is 5–20 μm, leading to moderate gas barrier properties and requiring precise sealing; the resistivity after modification is 0.2–0.4 Ω・cm², limiting the increase in electrolyzer current density.

3. Porous Composite Membranes: Upgraded Mainstream Material

Porous composite membranes are developed to address the high resistance and cross-contamination issues of pure PPS membranes, offering comprehensive performance upgrades and gradually becoming the mainstream choice for new high-end hydrogen production projects.

Material and Structure: Utilizing a composite structure of "PPS fabric support layer + ceramic polymer coating," the middle PPS filament fabric provides mechanical support, while the upper and lower surfaces are coated with ZrO₂/TiO₂ ceramic particles and polysulfone (PSU) and polyetheretherketone (PEEK) binders, forming a dense nanoporous coating.

Core Advantages: The ceramic particles have strong hydrophilicity, forming continuous ion channels with a sheet resistivity ≤0.3 Ω・cm²; the coating porosity is reduced to 0.05–0.2μm, significantly improving gas barrier properties and reducing the risk of cross-contamination.

Core Disadvantages: The coating process is complex, requiring high equipment precision; the cost per ton of membrane is 30%–50% higher than pure PPS membranes; the coating is prone to peeling and cracking during long-term operation, resulting in unstable performance; the core formula is monopolized by overseas companies, and domestic products still lag behind imports.

II. Future Technology Outlook

The current industry landscape is clear: PPS fabric membranes, with their mature processes and cost advantages, dominate large-scale industrial production and are the optimal choice at present; porous composite membranes are experiencing performance upgrades, adapting to high current density and new energy coupled hydrogen production, accelerating domestic substitution.

With advancements in materials and processes, membranes will continue to iterate towards low resistance, long lifespan, and low cost, further reducing the cost and improving efficiency of alkaline hydrogen production, ultimately facilitating the large-scale implementation of green hydrogen and providing core material support for global carbon neutrality and energy transition.

FAQ:

1. Who are we?
We are based in Anhui, China, start from 2011,sell to Southeast Asia,North America,Eastern Europe,South Asia.

2.Can you customize the rated power or voltage?
Yes, customizing products is acceptable.

3.Can your company provide whole system(fuel cell, Hydrogen production, hydrogen storage, hydrogen supply system)?
Yes, we can provide necessary accessories accordingly.

4. Why should you choose from us not from other suppliers?
We have an experienced professional technical research and development team. Control system matching ability/R&D and quality control ability. Price advantage brought by supply chain integration capabilities.