Open-cell titanium foam is a cellular titanium sheet: solid struts surround interconnected pores, not a sintered-fiber mat or a woven-wire cloth. In water electrolysis it is discussed as a porous transport layer (PTL), gas-diffusion medium or electrode support—most often on the PEM anode, where carbon paper is unsuitable because the anode potential would corrode carbon (Majasan et al., 2019). Foam is not the catalyst layer, and it is not a substitute for titanium fiber felt or titanium mesh. This guide covers the usual specification levers, how to read published pore-size and thickness results, and what to send for a quotation. It is not a ranking claim or a list of fixed HuiRui numbers.
Foam is not felt and not mesh
The three titanium forms on electrolyzer drawings answer different questions:
- Titanium foam has a cellular, open-pore structure. Buyers usually start with thickness, a pore-size figure (sometimes as pores per inch, PPI) and porosity. PPI is a linear count of pores along an inch; it is not a mean pore diameter from porometry, and it is not a filtration rating.
- Titanium fiber felt is a sintered fiber network. Start with porosity, thickness and the catalyst-side surface; see titanium felt porosity and thickness for PEM projects and titanium felt pore size, flow and PTL contact.
- Titanium woven mesh is specified by mesh count or opening and wire diameter; see titanium woven wire mesh: mesh count, wire diameter and opening.
Using one name when the drawing shows another structure is a common sampling error. If you are still choosing an electrolyzer type, our overview of ALK, PEM, AEM and SOEC electrolyzers explains where titanium parts are typical and where nickel is the usual choice.
Where titanium foam shows up
Majasan et al. (2019) list sintered titanium powder, expanded sheet, fiber felt and titanium foam among the titanium forms commonly discussed as PEM anode PTLs. The PTL sits between the catalyst-coated membrane and the flow field or bipolar plate. It has to admit water, release oxygen, and carry current and heat, so pore size, porosity, thickness and the contact face trade off against each other. Most published numbers come from sintered powder or felt rather than foam; they are useful context only when kept as study-specific results, not as targets on a HuiRui foam quotation.
A different job is using a block of open-pore foam as a flow distributor instead of a grooved plate. Khatib et al. (2021) compared serpentine, mesh and open-pore cellular foam flow channels in a PEM electrolyser. That is a flow-field question, not a thin transport-layer question.
Thickness, pore size, porosity and the other levers
Thickness. State the finished thickness you need, and whether it is a free (uncompressed) thickness or a thickness under a load already written on your drawing. Those labels are not interchangeable. Majasan et al. tested commercial sintered-powder PTLs about 1 mm thick. Lee et al. (2023) note that sintered titanium-powder PTLs are often about 1–1.4 mm, while the tape-cast titanium PTLs they made were about 200 μm. Those values describe the samples in those papers, not a HuiRui stock list.
Pore size. Send any number you already have and how it was defined: PPI, a stated mean pore diameter, or a measured distribution and method. Grigoriev et al. (2009), using sintered spherical titanium-powder current collectors, suggested about 12–13 μm mean pore diameter, 30–50% porosity and 50–75 μm powder size in that study, balancing capillary effects below about 10 μm against extra ohmic loss at larger pores. Majasan et al. compared four commercial sintered-powder PTLs about 1 mm thick with manufacturer mean pore diameters from 16 μm to 90 μm. In their cells the smallest-pore sample gave the best overall polarization because contact and ohmic resistance dominated; at 3.0 A cm−2 those same small pores showed the highest mass-transport resistance. Parra-Restrepo et al. (2020) found that a favourable sintered-powder PTL geometry also depends on current density, pressure, temperature and the catalyst layer. Lee et al. saw the same contact-versus-gas-removal trade-off in tape-cast structures: in that work a 60:40 titanium-to-PMMA mix with 60 μm pore-former beads outperformed a commercial powder PTL by 62 mV at 4 A cm−2. None of these figures is a standard foam specification for every stack.
Porosity. Porosity is the void fraction of a defined bulk volume. Two foams can share a similar porosity and still differ in window size and strut thickness.
Sheet size and edges. Give length × width or a cut-part drawing, plus any edge, flatness or tab requirement you already have.
Compression. Metal foams can change thickness under stack load. Quote a compressed thickness only if your documents already define the load and the method.
Coating, or none. Bare titanium can grow a poorly conductive oxide and raise anode contact resistance. Say whether you need a bare sheet, a noble-metal-coated substrate or a complete catalyst-coated electrode. Coating chemistry, loading and which face is coated are covered in iridium versus platinum coated titanium: mesh, foam or felt.
Foam versus felt: a quick comparison
| Form | Structure | Where it tends to fit | What to specify first |
|---|---|---|---|
| Titanium foam | Cellular open pores | Some PEM PTLs, gas-diffusion media and flow-through electrodes | Thickness, pore size (PPI or measured diameter), porosity if known, cut size, coated or bare |
| Titanium fiber felt | Sintered fibers | Common PEM anode PTLs | Thickness, porosity, catalyst-side finish (43391, 23714) |
| Titanium woven mesh | Woven wires | Current distributors and many tank anodes | Mesh count or opening and wire diameter (43415) |
Felt details belong on the felt pages linked above. Foam details belong on the enquiry for a cellular sheet.
What to send for a quote
You do not need a complete laboratory list to contact HuiRui. A sketch, a drawing, or an approximate size and duty is enough to start. The items below help when you already have them:
- The job: PEM anode PTL, flow-through electrode or support, flow-field insert, or another use.
- Thickness, and whether that number is free or under a load already on the drawing.
- Pore size if known (PPI and/or a measured mean pore diameter and method).
- Target porosity if your project already states one, and how it will be checked.
- Cut size or blank size, quantity, and whether you need samples first.
- Bare or coated; if coated, the type and which face(s), or a pointer to your coating specification.
- Any flatness, edge or inspection record required by the project.
We supply titanium foam, including sheets discussed for water-electrolyzer and hydrogen-production duty, as well as iridium-coated titanium foam and platinum-coated titanium foam. Related substrates include titanium fiber felt and titanium wire mesh. Dimensions, pore structure and any coating are confirmed per enquiry. Product pages may list illustrative ranges for quotation discussion; do not treat those ranges, or the literature results above, as verified cell performance for every design. Send the drawing and the items you already know, and we will reply with what we can make.
References
- J.O. Majasan et al., “Correlative study of microstructure and performance for porous transport layers in polymer electrolyte membrane water electrolysers by X-ray computed tomography and electrochemical characterization”, International Journal of Hydrogen Energy 44 (2019). https://doi.org/10.1016/j.ijhydene.2019.05.222
- S.A. Grigoriev, P. Millet, S.A. Volobuev and V.N. Fateev, “Optimization of porous current collectors for PEM water electrolysers”, International Journal of Hydrogen Energy 34 (2009) 4968–4973. https://doi.org/10.1016/j.ijhydene.2008.11.056
- K. Lee, G.Y. Lau, M. Sabharwal, A.Z. Weber, X. Peng and M.C. Tucker, “Titanium porous-transport layers for PEM water electrolysis prepared by tape casting”, Journal of Power Sources (2023) 232606. https://doi.org/10.1016/j.jpowsour.2022.232606
- J. Parra-Restrepo et al., “Influence of the porous transport layer properties on the mass and charge transfer in a segmented PEM electrolyzer”, International Journal of Hydrogen Energy 45 (2020). https://doi.org/10.1016/j.ijhydene.2020.01.100
- F.N. Khatib, T. Wilberforce, J. Thompson and A.G. Olabi, “Experimental and analytical study of open pore cellular foam material on the performance of proton exchange membrane electrolysers”, International Journal of Thermofluids 9 (2021) 100068. https://doi.org/10.1016/j.ijft.2021.100068
Related reading: Nickel foam, nickel fiber felt or nickel mesh: how to specify the structure.