How to Select a Titanium Porous Transport Layer for a PEM Electrolyzer

When selecting a titanium porous transport layer for a PEM electrolyzer, start with the two surfaces it touches: the anode flow-field plate and the catalyst layer. The PTL must deliver water, remove oxygen and maintain electrical contact under assembly pressure. Samples with the same nominal thickness can behave differently at these interfaces.

What Is a Titanium PTL in a PEM Electrolyzer?

A titanium porous transport layer (PTL) is a porous, electrically conductive component on the oxygen-producing side of a PEM water electrolyzer. One face contacts the anode catalyst layer. The other spans the flow channels and touches the raised sections of the plate, called lands.

The pores provide paths for water and oxygen, while the solid titanium provides a path for electrons. For an overview of the cell and its components, read Gitan’s guide to PEM water electrolysis.

Figure 1. Anode cross-section. Channels supply water and collect oxygen. Layer thicknesses are schematic.

How Does the Anode PTL Work?

H₂O   Water delivery. Feed water passes from the channels through connected pores to the anode catalyst. Beneath a plate land, water may also travel sideways. Evaluate a PTL together with the intended flow-field geometry.

O₂   Oxygen removal. Oxygen forms at the catalyst surface and exits through the pore network toward the channels. Water supply and oxygen removal share this network, so pore connectivity matters.

e^-   Electron conduction. Electrons released at the anode travel through solid titanium to the plate. Contact area and surface condition at each interface influence electrical losses.

Titanium Mesh vs. Titanium Fiber Felt

Ask what the supplier means by titanium mesh. Woven wire mesh, expanded metal and multilayer sintered mesh have different geometries. The illustration below shows woven mesh. For multilayer material, specify the construction of each layer and identify the face that contacts the catalyst.

Figure 2. Illustrative surface views of woven mesh and fiber felt. Actual pore dimensions and surface finish depend on the material grade.

Which PTL Specifications Should You Compare?

Compare measurements made under equivalent conditions. A mesh aperture and a felt’s mean flow pore size describe different features even when both are expressed in micrometers. Contact resistance also depends on the counterface and applied pressure.

What Should You Include in a PTL Sample Request?

Send the active area and outline drawing separately. An active area of 50 cm² gives the supplier the electrode area. The drawing adds finished dimensions, edge clearances, cut-outs and orientation. Include the assembly pressure, contacting materials and required sample quantity.

Frequently Asked Questions

What is the difference between a PTL and a GDL?

In this guide, PTL refers to the porous titanium component on the oxygen-producing anode. GDL means gas diffusion layer, a term used for porous media in fuel cells and sometimes on the hydrogen side of an electrolyzer. Confirm the cell side, material and contacting surfaces when reading a drawing.

Is higher porosity always better?

No. A larger void fraction can leave fewer solid contact points at the catalyst surface. Compare water delivery, oxygen removal and electrical contact together using the intended plate geometry and assembly load.

Can titanium mesh and felt of the same thickness be interchanged?

Matching nominal thickness is the first check. Compare compressed fit, catalyst support and contact resistance. Before approving a substitution, evaluate both samples using the same CCM, plate, assembly pressure and operating conditions.

Technical reading: Flow-field geometry and PTL properties and the effect of compression on PTL performance.