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Hydrogen Separation Membranes

Most people don't realize that the purity of Hydrogen sent into fuel cell for making electricity. (if your using that system Different to Stans) ​

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Will do the following
1. If it is Low Grade impure HHO hydrogen it will degrade life of Fuel Cell .

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So I decided to place this page here to raise knowledge and access to manufactures of Membranes for Hydrogen production and filtering.
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The is a lot of information available to people building the own cells simple email me with you requests. We can help with Designs and On going membrane supply.

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What Gas Diffusion Layer (GDL) do I use for a Hydrogen Generator (Electrolyzer)?

 

 

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.  Electrolyzer Membrane Electrode Assemblies (MEAs) and Catalyst Coated Membranes (CCMs).

 

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 danieldonatelli@hotmail.com 

and we will be happy to help.

Membrane Electrode Assembly (MEA) Activation Procedures

 

Dry Membrane Electrode Assembly

 

Why is an activation procedure or break-in necessary for a membrane electrode assembly(MEA)?  A large reason for performing an activation procedure or break-in is to properly humidify the membrane portion of the MEA that was dried out during the hot press stage of themembrane electrode assembly (MEA) production.  MEAs will not work well when they are not fully humidified (see article: Why is Humidity / Moisture Control Important in a Fuel Cell?).
 

How do I Humidify a Membrane Electrode Assembly (MEA)?

You can re-humidify the MEA by soaking it in deionized water.  Be aware that the membrane expands as it is hydrated, so it is possible that you will see some de-lamination of the gas diffusion electrode (GDE) from the Nafion membrane if you are using a 5-layer MEA that has the GDE bonded to it.  This shouldn’t significantly affect performance and you can still install the MEA into your stack or test cell even if portions of it are slightly de-laminated.

 

The other method to humidify the MEA is to install it in the stack or test cell and then run a break-in process in which it is operated in an air starved mode periodically.  Operate normally (with a suitable load applied) and then turn off flow on the Air/Oxygen side until the power drops significantly and begins to settle out (around 5 minutes).  Then reintroduce the air/oxygen flow until the power increases and stabilizes again.  Repeat this as necessary until there are no further performance gains.

 

What this is does is allow for the MEA to produce water (and power) as it consumes the residual oxygen in the system when the flow is removed, but not allow that humidity to escape with the gas flow (as it does during normal operation, to some extent).  The hydrophobic surface of the gas diffusion layer / gas diffusion electrode (GDL / GDE) helps to keep the moisture in the membrane without wicking it away – until it’s fully saturated, at which point the hydrophobic surface actually helps to push the excess water out of the GDL and into the gas stream without giving a good place to condense and “flood” the cell.
 

Membrane Electrode Assembly Activation Procedure

The start-up procedure for a new fuel cell membrane electrode assembly MEA may vary somewhat from application to application. What is important in any research or production environment is to be consistent with the break-in procedure that you use.  

 

How the MEA is initially broken-in can have long lasting effects on the ultimate performance of the MEA. Published procedures vary in specifics, but almost all follow a similar sequence:

  1. Initial Start-Up

  2. Load Cycling

  3. Final Performance

The US Fuel Cell Council (USFCC) published a standard for single cell testing that includes specific break-in procedures (beginning on page 15):

  • Fuel: Hydrogen, 1.2 Stoich, 100% RH

  • Oxidant: Air, 2.0 Stoich, 100% RH

  • Temperature (C): 80

  • Pressures (psig): 25

Initial Startup:  As required to reach 80C

  1. Cycle Step 1 (Perform Once): Hold 0.6V for 60 mins

  2. Cycling Step 2 (Perform 9 times): Hold 0.7V for 20 mins, than hold 0.5V for 20 mins

  3. Constant Current Operation: Hold at 200 mA/cm² for 720 mins (12 hrs)

Verify break-in status by repeating the polarization curve sequence three times, or as necessary, to ensure that the cell is broken-in. Remain at each sequence step for 20 minutes. The cell is considered broken-in when less than a 5 mV deviation from the previous polarization curve is recorded at 800 mA/cm². A wait period of 10 minutes should be observed between polarization curves. During this period, return the gas flow rates to the equivalent of 10 stoich at 200 mA/cm² and set the current to 800 mA/cm².


For additional questions or inquiries regarding the activation / break-in procedures of  membrane electrode assemblies (MEA) contact us, your membrane electrode assembly experts.

 

Also, do not forget to check out our standard membrane electrode assemblies here. If you would like a quotation for a custom membrane electrode assembly please contact one of our fuel cell specialists.

 

What Nafion Membrane Thickness is Right for an Electrolyzer / Hydrogen Generation?

 

 

Nafion Membrane

Nafion membranes come in many different thickness and types.  How do you know which to choose when designing an electrolyzer (hydrogen generator)?

Choosing the proper thickness depends primarily on the differential pressure you expect across the membrane (i.e. what pressure you will be generating the hydrogen at vs. the oxygen), the type of support the membrane will have, and the operating lifetime (both hours and on/off cycles).

 

Our Standard Choice:

We use Nafion 115 membrane, which is 0.005" thick, as our standard/default membrane for our electrolyzer MEAs.  We do so because it offers a great balance between a number of design considerations:

  • Thin enough for high-efficiency (thinner is less resistive & therefore produces hydrogen at a lower voltage)

  • Thick enough to handle 50+ psi differential pressure (depending on the support design)

  • Thick enough to decrease cross-over (H2 diffusing through the membrane from the H2 side to the O2 side)

  • Thick enough to have bulk that will yield good long-term stability of the membrane

 

When would you use a thinner membrane?

When the best efficiency is required and there won't be much differential pressure across the membrane.  We have made membranes using Nafion 212 (0.002" thick), Nafion 211 (0.001") and Nafion XL (~0.001"; chemically reinforced) that have all been shown to be exceptionally efficient.

 

What about thicker membranes?

Thicker membranes and fiber reinforced membranes are more appropriate for very high differential pressure applications (1000+ psi) or very long operating life (100,000+ hrs).

 

Some of these factors can also be mitigated with good mechanical design of the electrolyzer cell, good catalyst configurations, etc.

 

If you have any questions about what might be the best membrane for your hydrogen generation application, feel free to leave a comment or email us at danieldonatelli@hotmail.com

Material Kits

 

Which Fuel Cell Material is Right for Your Application? 

The Fuel Cell Material Kits are made up of a variety of products for the following categories:

  • Gas Diffusion Electrodes

  • Gas Diffusion Layers

  • Nafion Membranes

These are very useful for anyone who is testing different material for a specific application or even for educational purposes.

 

When buying a Material Kit you are not only getting a great variety but a discount as well! The fuel cell components offered in each type of material kit are available in larger quantities for the creation of fuel cells and fuel cell components as well.

How Much Hydrogen or Oxygen

Will my Electrolyzer Make?

 

 

There are a lot of design considerations that go into an electrolyzer that will dictate what pressure they can operate at, their efficiency, safety, etc.  Today I will let you worry about all the mechanical design and talk a bit about the principles behind the electrolyzer and what this means to you (the designer).  Everything below applies primarily to PEM water electrolysis, but much of it may apply to other electrolyzer types as well.  If you want to skip the explanation, you can go straight to the handy spreadsheet.

 

Current

As you know, electrolyzers convert water and power (electricity) into Hydrogen and Oxygen. The interesting part to me was that the amount of H2 or O2 the electrolyzer generates is determined solely by the current.

This makes sense when you look at the physics of the electrolysis cell.  Since current is defined as the flow of electrons (or protons) and a Hydrogen molecule is just 2 protons and 2 electrons, it follows that when you put a certain number of electrons across the membrane (current), it will generate an equivalent number of Hydrogen molecules.

The exact amount is 0.007 Liters/minute @ STP (aka standard Liters per min, or SLPM) of H2 for every Amp that is put through each cell (0.007 SLPM/A/cell)

In practice, this gives you two variables to play with: Current and Number of Cells.  For example.  If you wanted 7 SLPM of H2 you could design a single cell eletrolyzer and pump 1000 A through it (0.007SLPM/A/cell * 1000A * 1 cell) or you could design one with 10 cells and only have to put 100 A through it (0.007 * 100A * 10 cells).  This allows you to get a rough estimate of how many cells you might need based on the current available.

Also, since the Hydrogen and Oxygen production are dictated completely by the current, this can sometimes be a convenient way to control production rates without actually having to measure the gas production or rely on other parameters that may change with time.

 

 

Voltage

The voltage that it takes to provide this current determines the overall efficiency, and thus the amount of power (P=V*I) required to generate your Hydrogen and Oxygen.

The voltage each cell will operate at is an experimentally determined value that can vary depending on the properties of the MEA (Catalyst types, Membrane thickness), temperature, current density, mechanical design, etc.  At any given set of conditions, an MEA (Membrane Electrode Assembly) will have a Voltage vs Current parameters (usually called an IV curve).

 

These curves will have lower voltages at lower current densities.  This means less power per unit of gas generated.  But since you are also providing less current you will have to have larger active areas and/or more cells to generate the same total amount of gas (but at a lower total power).

Basically, this means that you can achieve higher efficiencies, but it usually increases the stack costs since you have more cells and therefore more components.  Of course, some systems can call for higher stack costs because it results in lower overall system costs (or mass) by allowing you to use convenient, lower cost power supplies, fewer solar panels, etc.

 

There are of course many other factors that go into the proper selection for your Electrolyzer project.

 

Current flow is either defined as electron flow (in conductors), “hole” movement (in P-type semiconductors), or ion movement in solution (as here, in electrochemistry.)

It follows that current can only defined as “proton flow” in the special case of H+ ion movement in solution. This may well be the case in one’s electrolyzer, but it is not GENERALLY true that “current is defined as the flow of electrons (or protons).

Electrolyzer Design Helper

 

There are a lot of design considerations that go into a fuel cell electrolyzer that will dictate what pressure they can operate at, their efficiency, safety, etc.  Today I will let you worry about all the mechanical design and talk a bit about the principles behind the electrolyzer and what this means to you (the designer).  

 

Everything below applies primarily to Polymer Electrolyte Membrane (PEM) water electrolysis, but much of it may apply to other electrolyzer types as well.

What is the Purpose of a Gas Diffusion Layer (GDL)?

 

 

Gas Diffusion Layer (GDL)

The Gas Diffusion Layer (GDL) plays several critical roles in a typical fuel cell application and is often integrated as part of the Membrane Electrode Assembly (MEA). Typical applications that use GDLs consist of Polymer Electrolyte Fuel Cells (PEMFC) and Direct Methanol Fuel Cells (DMFC). When a GDL is coated with a catalyst it is than referred to as a Gas Diffusion Electrode (GDE), which are sometimes sold or installed separately from the Membrane or MEA. 

Acting as an electrode is the easy part of the GDL/GDE, though.

 

What Does a Gas Diffusion Layer (GDL) Consist Of?

The GDL is a porous structure made by weaving carbon fibers into a carbon cloth (e.g. GDL-CT and ELAT) or by pressing carbon fibers together into a carbon paper (e.g. Sigracet, Freudenberg, and Toray).  Many of the standard GDLs that are produced today come with a Micro Porous layer (MPL) and hydrophobic treatment (PTFE).  The MPL and PTFE help with the contact to the membrane and with water management.  

 

The MPL typically provides a smooth layer with plenty of surface area for catalyst and good contact with the membrane.  The MPL often uses PTFE as a binder that increases hydrophobicity, which helps keep the water within the membrane from escaping – drying out the membrane and causing higher resistance (lower performance).  There is often an additional PTFE coating on the MPL surface to further augment this.

 

What Exactly Does a Gas Diffusion Layer (GDL) Do?

Membrane Electrode Assembly Diagram

GDL essentially acts as an electrode that facilitates diffusion of reactants across the catalyst layered membrane. The surface area and porosity of the GDL is what allows for the reactants in the channels of the bipolar plate to diffuse along the active area (catalyst area) of the membrane.  With the increased surface area that the GDL provides, transportation of electricity from each individual catalyst site in the Membrane Electrode Assembly (MEA) to the current collectors increases.

 

The GDL is also the component that handles the fuel cell moisture control.  It does this by consistently helping to remove the by-produced water outside of the catalyst layer and prevent flooding chambers. The GDL also helps keep some water on the catalyst layer surface to improve conductivity throughout the membrane.  It is also important to note that the GDL allows for heat transfer during cell operation as well.

 

Important consideration must also be made in regards to the mechanical properties of the GDL material since it is often compressed or partially compressed when the fuel cell stack is assembled.  This compression can act as a bit of a “spring” to help accommodate for some of the thermal expansion larger fuel cell stacks can see in operation.  

We found in our work that there was not a very good single source that compared the properties of the most common GDL materials (and the manufacturers often use different units and measures).

 

 We’ve compiled a Gas Diffusion Layer comparison table of some of the more common GDL materials so you can quickly compare properties and help decide which option might be best for you.  Let us know if you have any additions, questions, etc.  And feel free to share it with friends and colleagues if you find it useful!

 

Which Gas Diffusion Layer (GDL) is right for you will depend on the specifics of how your fuel cell hardware, MEAs, and sealing are all designed.  If you would like to know more contact danieldonatelli@hotmail.com or visit our fuel cell store and browse the current Gas Diffusion Layers and Gas Diffusion Electrodes that we have in stock!

Why is Humidity / Moisture Control Important in a Fuel Cell?

 

Gas Diffusion Layers

Gas Diffusion Layers (GDL) are an important part of water management in a hydrogen fuel cell.

The root of all of this is that Nafion membranes must stay hydrated to function properly.

 

If they are not fully humidified the conductivity decreases and therefore more of the electricity is converted directly to heat before it leaves the membrane (I2R heating). If it gets too dry it basically stops functioning as a proton transporter.  All this sounds great since a Hydrogen Fuel Cell consumes Hydrogen and Oxygen to generate electricity and water, so you would think there should be plenty of it around right? Well there is, and that's the other problem.

 

The Hydrogen and Oxygen (Air) gasses need to get to the catalyst sites and the membrane in order to be converted into electricity. However, if there is any liquid water at the catalyst layer it covers up the catalyst and the gas cannot get to it, basically making the catalyst that's underwater useless – effectively reducing the active area that is available to convert H2and O2 to electricity.

 

This is where the magic happens with the GDL. The GDL materials are all specially formulated with hydrophobic coatings and permeability properties. These are all designed to help get the water away from the catalyst layer while it's still in vapor form and not allow it to form to liquid until it is well clear of the catalyst sites. This is even further complicated when you consider that fuel cells are operating in widely varying environments. Some need to work in hot/dry desert environments while others need to work in very humid environments.

 

The various manufacturers each have various GDL types that they have optimized for different operating parameters and different physical properties (we'll get into those another time). Good thing we work with most major GDL manufacturers (and many of the smaller ones as well) so we can work with you to find which GDL will work best for you!

Gas Diffusion Layers (GDL) Electron Extraction?

 

The Gas Diffusion Layer (GDL) is a very important supporting material in a Membrane Electrode Assembly (MEA). Gas diffusion layers are a porous material composed of a dense array of carbon fibers, which also provides an electrically conductive pathway for current collection. GDL plays an important role of electronic connection between the bipolar plate with channel-land structure and the electrode. In addition, the GDL also performs the following essential functions: passage for reactant transport and heat/water removal, mechanical support to the membrane electrode assembly (MEA), and protection of the catalyst layer from corrosion or erosion caused by flows or other factors.

 

Physical processes in GDLs, in addition to diffusive transport, include bypass flow induced by in-plane pressure difference between neighboring channels, through-plane flow induced by mass source/sink due to electrochemical reactions, heat transfer like the heat pipe effect, two-phase flow, and electron transport. 

The two types of gas diffusion layers most commonly used are carbon paper and carbon cloth. Both are carbon fiber based porous materials: carbon paper is non-woven, while carbon cloth is woven fabric, thus no binder is needed.

 

Gas Diffusion Layer's Main Functions:

1. A gas diffused pathway from flow channels to the catalyst layer.
2. Help to remove by-produced water outside of the catalyst layer and prevent flooding.
3. Keep some water on surface for conductivity through the membrane.
4. Heat transfer during cell operation.
5. Provide enough mechanical strength to hold membrane electrode assembly from extension caused by water absorbance.

 

Check out our Tech Article: What is the Difference Between Carbon Paper and Carbon Cloth Based Gas Diffusion Layers (GDL)?

 

View or Download all of our Gas Diffusion Layer (GDL) property sheets here.

What is the Difference Between Carbon Paper and Carbon Cloth Based Gas Diffusion Layers (GDL)?

 

 

Carbon Paper versus Carbon Cloth Gas Diffusion Layers GDL

Carbon Paper Gas Diffusion Layers

Carbon Paper Gas Diffusion Layers (GDL) (e.g. Sigracet, Freudenberg, Toray, etc) tend to be thinner and more brittle than Carbon Cloth Gas Diffusion Layers (e.g. ELAT™, GDL-CT).  Each type has a different mass transport, porosity, hydrophobicity, and conductivity.  

Papers such as Toray are quite hard and brittle, with very little compressibility.  These are good for designs where a tighter tolerance is permitted in the compression and where the thin GDL is a critical factor.  Since they are so brittle, care must be taken when handling them in order to not break corners or otherwise damage the GDL.

There are a few other GDL’s  which are much more flexible (e.g. Sigracet, Freudenberg) and have a little more compressibility than Toray paper, which in turn makes them much easier to handle. They also do not chip or break as easily as Toray paper while still being available in thin sizes. Some GDLs are very hard and brittle with little compressibility (e.g. Toray); others are much more pliant/flexible but still don’t have much compressibility (e.g. Sigracet, Freudenberg).  Also, papers may or may not have Microporous Layers (MPL) and/or additional hydrophobic (Teflon) coatings.

 

Carbon Cloth Gas Diffusion Layers

The Carbon Cloth based GDL materials (e.g. GDL-CT, ELAT LT 1400) are the most flexible and are generally quite mechanically robust, but are also the thickest.  These are typically designed to have a fair amount of compression when assembled in the stack (anywhere from ~10% to 60% of the GDL thickness) and can act somewhat as compressible “springs” in the stack design.

We’ve put together a convenient table listing the properties of some of the more common GDL materials.  I hope it is useful in helping you make your selection.  Of course, you’re always welcome to AskUs@FuelCellsEtc.com if you need more specific guidance in your application.  There are many other GDL material types available as well (as custom options) that we are more than happy to assist you with as well.

Click here to visit our fuel cell store (Carbon Paper Gas Diffusion Layers and Carbon Cloth Gas Diffusion Layers).

 

Gas Diffusion Layer Comparison Table

Download the gas diffusion layer comparison table located below here. Click on the Gas Diffusion Layers (GDL) with red font to be directed to our online store and buy them today! If there is a GDL that you see that we do not have on our online store, contact us, and we will respond to you with a quotation in less than 24 hours.

 

*Toray paper, SpectraCarb, AvCarb and more will be available soon on our online store.  Contact us to reserve yours today!

 

Carbon Paper

Carbon Paper Gas Diffusion Layers(GDLs) are designed to meet the various requirements in Hydrogen (PEMFC) and Direct Methanol Fuel Cells (DMFC). These Gas Diffusion Layers are manufactured by proprietary non-woven technology.

 

Contact one of our fuel cell specialists about our other GDL Carbon Papers:

  • Sigracet SGL - 25BC

  • Sigracet SGL - 35BC

  • Toray Paper - H - 060

  • Toray Paper - H - 090

  • Toray Paper - H - 120

  • Freudenberg - H2315 - C4

 

Carbon Cloth

 

Carbon Cloth Gas Diffusion Layers (GDLs) are designed to meet the various requirements in Hydrogen (PEMFC) and Direct Methanol Fuel Cells (DMFC). These Gas Diffusion Layers are manufactured by proprietary woven technology.

Multiple Older Versions of ELAT™ - ETEK also available:

  • ​ELAT 2300W

  • ELAT 2500W

  • ELAT LT 2510W

  • And more! 

Catalyst

 

Platinum and Platinum Ruthenium Alloy, the most effective catalysts for oxidation and reduction reactions, when dispersed evenly in carbon powder, increase reactive surface area significantly and provide an ideal catalyst for many electrochemical processes.

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