Material Insights · Understanding the Material World

Electrolysers: Equipment and suppliers

Stacks, rare iridium and the half that is not the stack

What this tab covers For each method, the main pieces of equipment, who makes them (by region) and what they are made of (bill of materials).

The stack is where the chemistry happens, but rectifiers, gas separators, purifiers and compressors make up roughly half of system cost.

PEM electrolysis

PEM stack126723

Splits water at the membrane; the anode side must resist acid at about 2 V.

Europe ITM Power, Siemens Energy, Nel United States Plug Power China LONGi Hydrogen, Sungrow Hydrogen
Bill of materials
  • Catalysts: Iridium anode, platinum-on-carbon cathode; 3.0 mg PGM per cm2 (0.8 g/kW) in 2022, target 0.125 mg/cm2
  • Membrane: PFSA (Nafion type)
  • Porous transport layers and bipolar plates: Titanium or stainless steel, coated with gold or platinum
  • Stack as a whole 40-60% of system capital cost

Alkaline electrolysis

Alkaline stack (pressurised or atmospheric)57920212223242526

Hundreds of cells in a filter-press stack; a 20 MW module has about 300 cells.

Europe thyssenkrupp nucera, Nel, Sunfire, John Cockerill China LONGi Hydrogen, Peric, Sungrow Hydrogen, Envision
Bill of materials
  • Electrodes and bipolar plates: Nickel-coated stainless steel
  • Separator: Zirfon (zirconia in polysulfone)
  • Electrolyte: 30-40% KOH
  • Porous layers: Nickel foam
  • Stack: Manufactured at 45-65 USD/kW at high factory use 50-60% of uninstalled system cost

Solid-oxide electrolysis

Solid-oxide cell stack679111925

Ceramic cells split steam at high temperature.

United States Bloom Energy Europe Sunfire, thyssenkrupp nucera with Fraunhofer IKTS (roadmap under review in 2026)
Bill of materials
  • Electrolyte: Scandia- or yttria-stabilised zirconia
  • Electrodes: Nickel-based fuel electrode; LSCF (lanthanum strontium cobalt ferrite) air electrode
  • Interconnects: Crofer 22 APU steel interconnects; manganese-cobalt oxide (MCO) coated steel current collectors

Chlor-alkali membrane electrolysis

Bipolar membrane electrolyser1011

Stacks of cell elements that make chlorine, caustic soda and hydrogen.

Europe thyssenkrupp nucera, Industrie De Nora
Bill of materials
  • Cell element: About 2.85 m2 active area per element in the BM design; titanium anode side and nickel cathode side with coated electrodes and a perfluorinated ion-exchange membrane

Aluminium smelting

Reduction cell (pot) and pot line12161729

Steel shell lined with carbon cathode blocks, holding molten cryolite and aluminium; hundreds of cells are wired in series.

Rest of world EGA (DX, DX+ Ultra; UAE), Rio Tinto (AP cells) China GAMI and SAMI (Chinalco group design institutes)
Bill of materials
  • Anodes: Prebaked carbon from petroleum coke and pitch, about 0.43 t per tonne of aluminium
  • Cell design: 400-600 kA; about 12.1-13.1 DC kWh/kg

Sources

  1. Technical Targets for Proton Exchange Membrane Electrolysis US Department of Energy, Hydrogen and Fuel Cell Technologies Office, 2023
  2. DOE Hydrogen Program Record 22002: Historical Cost Reduction of PEM Electrolyzers US Department of Energy, 2022
  3. Underutilised electrolyser factories threaten hydrogen cost reductions, says IEA (reporting Global Hydrogen Review 2024) H2 View, 2024
  4. Water Electrolyzers and Fuel Cells Supply Chain: Supply Chain Deep Dive Assessment US Department of Energy, 2022
  5. How Can India Indigenise Hydrogen Electrolyser Manufacturing? (Annexure) Council on Energy, Environment and Water (CEEW), 2024
  6. thyssenkrupp nucera General Investor Presentation, May 2026 (company claims) thyssenkrupp nucera, 2026
  7. The right chlor-alkali electrolysis technology for your needs thyssenkrupp nucera, 2024
  8. thyssenkrupp nucera Annual Report 2024/2025 thyssenkrupp nucera, 2025
  9. Factsheet: Aluminium smelting with use of low-carbon electricity GIZ, 2025
  10. AP60 and APXe smelting technology factsheet (company data) Rio Tinto AP Technology, 2015
  11. History and Recent Developments in Aluminum Smelting in China (Gao, Wang, Shi, Hu), 35th ICSOBA Conference ICSOBA, 2017
  12. Bloom Energy Corp Form 10-K for fiscal year 2025 Bloom Energy / US SEC, 2026
  13. Electrolyzer Supply Chain Readiness Level (SCRL), 2024 Annual Merit Review poster NREL / Argonne National Laboratory for US DOE, 2024
  14. The IEA's Global Hydrogen Review 2025: green hydrogen ramp up is slower than we wanted, but it is happening all the same Green Hydrogen Organisation (GH2), 2025
  15. BNEF reveals top ten hydrogen electrolyser makers in the world by deliveries in 2024: six are Chinese Hydrogen Insight (reporting BloombergNEF), 2025
  16. SMM Survey: Hydrogen Energy Weekly Electrolyzer Industry Review, 16-22 January 2026 Shanghai Metals Market (SMM), 2026
  17. China unveils higher-capacity H2 alkaline electrolyser (Peric) Argus Media, 2022
  18. Sunfire 2025: scaling, partnerships and European strength (company news) Sunfire, 2025
  19. John Cockerill finishes 5MW electrolyser using McPhy-acquired assets gasworld, 2026
  20. EGA's technology Emirates Global Aluminium (company claims), 2026