Reimagined and Revamped. Fighting the spread of nonsense often feels like a Sisyphean task. However, the joy is in making the information available, not the hope of conversion.

Platinum Free Fuel Cells

Just saw this pop up in my New Scientist feed. Here is the headline:

Platinum-free fuel cell promises cheap, green power

My first reaction when I saw that was, "No! No! No!" and then I got mad again that the technical press just seems to not care anymore. What am I ranting about? Well lemme explain.

I have talked about fuel cells before. Well mostly one fuel cell in particular. I don't want to go over what they are or the specifics of how they work again. There are great resources on the net for that. for this post, you will need to go to those links to freshen up on what a fuel cell is, and understand the difference between power and energy is. Wikipedia has a nice picture of a PEM fuel cell here it is.


The most common proton exchange membrane (PEM) fuel cell has a layer of catalyst on either side of a membrane. This catalyst is usually Platinum, but could also have some palladium and/or ruthenium in it to achieve different properties. Scientist have been futzing with the catalyst for decades to try to achieve higher and higher power densities (the amount of power per square centimeter of membrane). To some degree they have done this.

Another aspect of fuel cells that has improved is the efficiency of fuel cells. Efficiency is a measure of the amount of energy pulled out of the fuel and used for work (or useful heating) relative to the theoretical energy contained within that fuel. Companies like MTI Microfuel cell has claimed 30% for their microfuel cells (because they get 1800 Wh/kg of fuel, whereas the theoretical limit of methanol is 6000), whereas other PEMs and other fuel cell systems can claim 60% or higher. The only reason a fuel cell is considered green is because it should have greater efficiency than an engine or other fuel burning competing method. If a fuel cell has crappy energy efficiency its simply not a green product.

OK, so what is wrong with the New Scientist article? The claim is that lowering the platinum cost of a fuel cell will lower the cost of the fuel cell. The article claimed that the reason to use platinum is because:
Platinum has so far been the metal of choice because the membranes used in fuel cells create a very acidic environment, and the metal is stable in such corrosive conditions.
That may be technically correct but it is hardly the sole reason for using platinum. The bigger reason is that no other catalyst gives as high a power density or energy efficiency. Besides, the membranes don't "create a very acidic environment", they are acidic. The acidity is what makes the protons go through the membrane while the electrons go around.

So then the next claim comes:
Now, though, Lin Zhuang's team at Wuhan University in Hubei province, China, has designed a new membrane that is alkali, not acidic - making it possible to use a much cheaper, nickel, catalyst.
Again, not technically wrong. I'm sure this guy has done this. What this is saying is that instead of a membrane in which protons move from one side to the other, negative ions, called anions, like hydroxyls (OH-) are moving from one side to the other. But it is hardly news worthy. Acta sells an anion exchange membrane from Tokuyama. And there have been others. The Medis fuel cell, while it does not have a polymer membrane, it too was a alkaline fuel cell.

Alkaline fuel cells have been around for decades. In fact the first fuel cells that went up to space we also alkaline fuel cells. They do have the advantage that they do not need platinum to achieve their highest power density, they can use nickel or iron. But the alkalinity of the Zhuang fuel cell and the fact that they have an anion exchange membrane are hardly news.
The team's new polymer proves easy to make into fuel-cell membranes, and can also be mixed with the catalyst itself - this increases the contact between the two components and boosts efficiency.
Uhhh. the PEM membranes can also come in a form that is a liquid and be mixed with catalyst for better contact. Not news.

Previous attempts to change the acidic conditions inside fuel cells involved using liquids, not solids, says Zhang, but they risked forming carbonate deposits that can clog up the cell.
Apparently Zhang is not keeping up with the literature. There have been previous alkaline membranes.

A working prototype of the new low-cost fuel cell shows a "decent" performance of 50 milliwatts per square centimetre at 60 °C. "The power output is still lower than that of fuel cells using platinum, but such a comparison may not be appropriate because platinum fuel cells have been studied and optimised for decades," Zhuang says.
Yes and the catalysts for alkaline fuel cells have been worked on for decades also. Not news.

The part that gets me is the idea that platinum is the major cost of a fuel cell. Its simply not. Lets find a fuel cell for sale. Here is one.

This sucker can put out 330W and it weighs in at 1.7 Kg. How much catalyst is that? Well we need to know a few things.

Active area per cell: 19.4 cm2
Number of cells: 60
Total Active Area: 1164 cm2
Pt loading: 0.7 mg/cm2

So the entire amount of platinum in this system is: 815 milligrams.

How much does that cost? As of this writing platinum is costing 830 dollars per ounce. or 26 dollars per gram.

So the entire cost of all the platinum for this entire 3000 dollar system is: 22 dollars.

See what I mean? Even if you double the cost of the platinum to gain performance, and then double it again because it needs to be refined to very small and pure particulate. We are still less than 100 dollars of the 3000 dollar system.

The cost of refined nickel isn't free either. I get antsy whenever I see claims of fuel cell costs dropping because someone figured out a way around the use of platinum. In a fuel cell system, the plates need to be made, the plates need to be assembled with the membrane and gas diffusion layers and gaskets between them. Then the fuel cell stack needs to be installed in a system which has controls and fuel ports, pumps and valves. You get the picture.

My last gripe about that useless article is the following...

Not once was efficiency mentioned. Not once. So how can any sort of claim about "greenness" be made? If the efficiency is not above at least 45% I say you don't get to use the word "Green".

9 comments:

On 12/16/08, 7:41 AM , Sceric said...

smile,

as an engineer in a geologist- and management-rich environment I know that feeling you express there. Our guys want to invest in geothermal energy (Greek island) instead of first investing in a new, much more efficient generator (or even better for our purposes a cogeneration unit)
Thanks for the as always detailed summary.
Sceric

 
On 2/7/09, 4:33 PM , Anonymous said...

How does "So the entire cost of all the platinum for this entire 3000 dollar system is: 22 dollars." relate to(someone's wrong):

"More than half the cost of fuel-cell stacks comes from platinum, according to the Department of Energy." www.technologyreview.com/energy/22074/

 
On 2/7/09, 6:30 PM , Techskeptic said...

I'm not sure what your question is (besides an appeal to authority). I read you article which doesnt explain how they got their number, they just appealed to an authoity without a link. Meanwhile if you can point to where my assumption or calculation was wrong, feel free to point it out.

One thing to note, my numbers relate to a fuel cell system. Your link talks about platinum in a fuel cell stack. That is one big difference that totally ignore the complexity of the system. Regardless its still wrong, the thing keeping fuel cell stack costs high is lack of production. Platinum will become a problem after the costs of bipolar plates, GDLs, gasketing, endplate and manifold hardware, and proton exchange membrane come down. Its hardly the strong issue right now, there is hardly any platinum in there (relative to the cost of everything else).

 
On 2/8/09, 7:39 AM , Kelly said...

What you say sounds sensible, but Google 'DOE platinum fuel cells' and most of the links seem about eliminating platinum from FCs per it's high proportion of the cost - stack or system.

Without further examples and links, the public more likely believes the Dept. of Energy.

 
On 2/8/09, 8:56 AM , Techskeptic said...

This is easy... there are 3-7 grams of Pt in a catalytic converter And yet, those sell just fine (and get stolen just fine, when platinum prices are high).

How much Platinum in a fuel cell cars? Well those fuel cells put out about 100 kW. So that would be a fuel cell 333 times bigger than in my example.

So yeah, over 7000 dollars is due to the platinum. But the cost of the clarity is often reported to be 10,000,000 dollars.. You can't even buy one if you wanted (because fuel cells generally have crappy reliability, they will only lease)

So, is getting rid of the cost of platinum really the cost barrier here? Keep in mind, this is an excellent fuel cell. The power density of the fuel cell is higher than what I have done in my example which brings down the Pt cost even more.

I don't know how to show my point better than with math and links to where I got my numbers. Appeals to authority are common and sadly powerful. Its how we let ourselves go to war for no reason.

Platinum is a red herring, it is NOT the reason that fuel cell cars cant currently make it. The costs of the rest of the fuel cell have to come down and the reliability needs to greatly improve (good ones last 10,000 to 40,000 hours if stationary, auto use is as low as 4000 hours)

That same article estimates the cost of 100kW auto fuel cell to be 750,000 dollars. So can we really sit here and think that platinum is our problem?

So yeah, to swap out the full cost and functionality of an engine, the Pt use would have be be reduced, but it is hardly the important problem currently. I hope we get to a day that we can truly point at the price of platinum. We are not there, not even close.

 
On 2/8/09, 10:23 AM , Kelly said...

Now I'm convinced - platinum costs are a minimal FC component.

Perhaps, because fuel cells are described like refilled batteries, no one can comprehend why the costs are so high and platinum cost seems easiest to blame.

 
On 2/8/09, 10:24 AM , Kelly said...

Now I'm convinced - platinum costs are a minimal FC component.

Perhaps, because fuel cells are described like refilled batteries, no one can comprehend why the costs are so high and platinum cost seems easiest to blame.

 
On 2/8/09, 10:33 AM , Techskeptic said...

Kelly,

it took me 500 words to say that same thing. :) Thanks for visiting.

 
On 6/9/11, 1:12 PM , Canada Viagra said...

WEll now I can see the difference and I support your viewpoint. I think this is not a good idea, but somebody already took the decision and we can't do anything to go back.