We've spoken already about Gas Diffusion Layer (GDL) selection for a Fuel Cell; today we will cover some GDL considerations for Electrolyzers.
The Hydrogen side (Cathode) of an Electrolyzer (EZ) can be almost any gas diffusion layer GDL (or even no GDL) that you would like and that fits your own mechanical design. This can be common GDL materials like Toray Paper, Sigracet, Freudenberg, AvCarb, etc. The Catalyst layer can either be applied to the membrane (as in a 3-layer or Catalyst Coated Membrane (CCM)) or applied to the GDL material itself. Our standard EZ MEAs come as a 3-layer (CCM) that allows you to select the GDL material for both the Anode and Cathode side that best fits with your stack design.
The Oxygen side (Anode) is a little trickier. On the Oxygen side, you cannot use carbon-based GDL materials. This is due to the electrochemical properties of carbon and the process of electrolysis - the carbon will be oxidized and converted into CO2. The carbon GDL will quickly be consumed, which will then leave a physical gap that will result in very poor electrical contact with the Membrane Electrode Assembly (MEA). This all means that the electrolyzer will essentially stop operating, or at the very least operate very inefficiently.
The Anode GDL or flow field material must be conductive, corrosion resistant, non-ion leaching and allow for easy water flow to the MEA (most PEM electrolyzers are Anode fed). Our preferred material for the anode side of electrolyzers is a thin titanium screen which we coat with a very thin layer of platinum. We call this Platinized Titanium (PtTi). The platinum content on the screen is not high enough to act as a catalyzed layer, but instead makes the titanium last longer at a lower resistance than bare titanium would. Fuel Cell Store offers several versions of Platinized Titanium in the form of Platinized Titanium Screen, Platinized Titanium Fiber Felt, High Porosity Platinized Titanium Fiber Felt and Platinized Ultra-Thin Titanium Porous Transfer Layer.
However, depending on your application, un-platinized Titanium screens or frits are suitable, as are high-quality Stainless Steel (even better if it's gold coated), or Nickel Wire Mesh for an Alkaline environment. Some materials you DO NOT want in your electrolyzer, or even in contact with the water in your electrolyzer are: copper, brass, bronze, etc.
If you have questions about the best GDL for your application, feel free to email our technical support team at email@example.com