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 3-layer (CCM) style that allows you to select the GDL material for both the Anode and Cathode side that best fit with your stack design.
The Oxygen side (Anode) is a little more tricky. 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 give a very poor electrical contact to the Membrane Electrode Assembly (MEA). This all means that the electrolyzer will essentially stop operating, or at the very least operate at very, very poor inefficiencies.
The Anode GDL or flow field material must be conductive, corrosion resistant, non-ion leaching and allow easy water flow through it to the MEA (most PEM electrolyzers are Anode fed). Our preferred material is a thin Titanium screen which we coat with a very thin layer of Platinum. We call this Platinized Titanium (PtTi) Screen. The Platinum makes the Titanium last longer at a lower resistance than bare Titanium would.
However, depending on your application, raw Titanium screens or frits are suitable as are high quality Stainless Steel (even better if it's gold coated). Some materials you DO NOT want in your electrolyzer, or even in contact with the water in your electrolyzer are: copper, brass, bronze, etc.
As always, if you have any questions please drop us a line at AskUs@FuelCellsEtc.com and we will be happy to help.