Hydrogen Energy's New Darling: How Foam Iron-Nickel Alloy Reshapes Hydrogen Production Electrolyzers

1. The New Era of Hydrogen

Since its discovery in the 16th century, hydrogen has been considered a crucial clean energy source due to its abundance, high energy density, and green, low-carbon properties.

Currently, hydrogen production processes are categorized by their carbon emissions into gray hydrogen, blue hydrogen, and green hydrogen. Among these, green hydrogen, produced by electrolyzing water using renewable energy, emits no greenhouse gases or harmful substances and boasts high purity. It is the cleanest method of hydrogen production and represents the primary future direction for hydrogen energy.

Green hydrogen is primarily obtained through water electrolysis, where an electrolyzer splits water into hydrogen and oxygen. There are currently four main electrolyzer technologies: ALK (alkaline water electrolysis), PEM (proton exchange membrane electrolysis), SOEC (solid oxide electrolysis cell), and AEM (solid polymer aNion exchange membrane electrolysis).

In the context of global carbon neutrality, green hydrogen has undeniably become a key area in energy transition. The ability of electrolyzer technology to further reduce costs and enhance efficiency is critical to its future success in this vital field.

2. The Mainstay: Alkaline Electrolyzers

ALK (alkaline water electrolysis) for hydrogen production takes place in an alkaline electrolyte environment, typically using KOH or NaOH solutions. The biggest advantage of this electrolysis technology is that both the anode and cathode plates do not contain precious Metals, resulting in the lowest electrolyzer cost. Furthermore, this type of electrolyzer is the most commercially mature, with extensive operating experience, and dominates the market. Key performance indicators of some domestic critical equipment have reached international advanced levels, offering large-scale hydrogen production per cell, making them easily adaptable for grid-powered electrolysis.

An alkaline electrolyzer primarily consists of components like end plates, gaskets, bipolar plates, Electrode plates, and diaphragms. The electrolyzer comprises dozens or even hundreds of electrolysis cells, pressed together by screws and end plates to form a cylindrical or square shape. Each electrolysis cell, delineated by two adjacent plates, includes six parts: positive and negative bipolar plates, an anode electrode, a diaphragm, a sealing gasket, and a cathode electrode.

Crucially, the alkaline electrolyzer electrode is where electrochemical reactions occur and is key to determining the electrolyzer's hydrogen production efficiency. Most electrodes used in large domestic alkaline electrolyzers are nickel-based, such as pure nickel mesh, foam nickel, or pure nickel mesh/foam nickel substrates coated with highly active catalysts. Among these, foam nickel is inexpensive and a mature product. Its electrode material is filled with numerous micropores, offering a vast surface area. This significantly increases the contact area between the solution and the electrode, shortens mass transfer distance, and greatly improves electrolysis reaction efficiency.

Foam iron-nickel alloy material outperforms traditional nickel-based materials, providing more active oxygen evolution sites, and its catalytic efficiency is significantly higher. It is a "masterstroke" for alkaline water electrolysis to further break through and advance. According to authoritative tests, under actual working conditions, the efficiency of alkaline water electrolysis using foam iron-nickel is superior to traditional nickel mesh. Based on current domestic and international cutting-edge research, DC energy consumption can be as low as 4.0-4.3 KWH/standard cubic meter, with energy efficiency reaching 80-85%.

3. The Dawn of AEM Electrolyzers

Solid polymer anion exchange membrane (AEM) water electrolysis is a hydrogen production process that uses a lower-cost anion exchange membrane as a separator, low-concentration alkaline solution or pure water as the electrolyte, and non-precious metal catalysts for the reaction.

In AEM electrolyzers, the anode typically consists of transition metal oxides (e.g., nickel oxide, cobalt oxide), while the cathode is generally made of precious metals or their alloys, such as nickel, platinum, or palladium.

The reaction at the anode is: 4OH−−4e−→O2​↑+2H2​O The reaction at the cathode is: 2H2​O+2e−→H2​↑+2OH−

The 4OH− mentioned here are the anions emphasized in this process. Under the action of the anion exchange membrane, the OH− produced at the cathode can migrate to the anode, increasing the OH− concentration at the anode side, leading to more oxygen and water generation at the anode. This naturally leaves a purer hydrogen product at the cathode.

The primary role of the cathode and anode materials is to catalyze the water splitting reaction and to efficiently output the produced hydrogen and oxygen. Therefore, both cathode and anode materials must possess strong catalytic activity and porosity. For the smooth progression of electrode reactions, cathode and anode materials must also have high anion and electron conductivity.

Currently, the most widely used cathode materials are nickel alloys, and anode materials are primarily nickel-iron alloys. Iron and nickel not only exhibit strong catalytic activity for water splitting but are also widely available and low-cost. Since AEM does not operate in highly corrosive environments, it does not require precious metal catalysts like iridium or titanium in the anode and cathode materials. This significantly reduces the manufacturing cost of AEM equipment, and its performance is not inferior to that of PEM technology, making it the mainstream direction for newly developed hydrogen electrolyzers worldwide.

4. Riding the Wave: The Rise of Foam Iron-Nickel

Whether for the current mainstream ALK (alkaline electrolysis) or the emerging AEM technology, foam iron-nickel offers unique application advantages and broad prospects.

Material Characteristics: Revolutionary 3D Mesh Design

• Ultra-high specific surface area:With pore sizes ranging from 20-450 μm and a porosity of ≥98%, its active surface area is hundreds of times larger than planar electrodes. This significantly boosts reaction rates, dramatically increases the contact area between the solution and the electrode, shortens mass transfer distance, and vastly improves electrolysis reaction efficiency.
• Effective catalysis: The surface of foam iron-nickel is coated with nickel-based and iron-based catalysts. These catalysts aid in the water electrolysis reaction, which splits water into hydrogen and oxygen.
• Structural support:The three-dimensional structure of foam nickel provides excellent support, helping to maintain the stability and structural integrity of the electrode, ensuring long-term operation.
• High conductivity:Both iron and nickel are good electrical conductors, and the three-dimensional structure of foam iron-nickel provides a high surface area, aiding in current distribution.

Catalyst Layer Application

Currently, electrolyzer catalyst layers primarily include the anode catalyst layer (OER-CL) and the cathode catalyst layer (HER-CL), which facilitate the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Since both OER and HER exhibit kinetic inertness, catalysts are typically loaded onto the electrodes to enhance reaction activity and reduce energy consumption. This is the function of the catalyst layer (CL). Because Ni-based catalysts show high activity and excellent corrosion resistance in alkaline media, and are more stable than other transition metals (such as Fe, Co), they are widely used as both OER and HER catalysts. Due to its high oxygen affinity, Fe tends to adsorb OH− species and is therefore often used as an OER kinetic promoter. Foam nickel-iron alloy material, which combines the properties of NiFe metals, shows significant advantages when used as an anode material for hydrogen production.

Diffusion Layer Application

The gas diffusion layer (GDL) is primarily used for gas diffusion—hydrogen at the cathode and oxygen at the anode. Additionally, due to its metallic conductivity and thermal conductivity, it also facilitates electron and heat transfer, thus being known as the porous transport layer (PTL). Currently, foam nickel is widely used as a diffusion layer material in the market. Furthermore, high-quality, cost-effective foam iron-nickel is now a more economical choice.