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New Catalyst May Be a Boost For Fuel Cells
Roland Piquepaille writes "Researchers at the University of Houston (UH) have developed a new platinum-based catalyst for fuel cells that is at least four times more efficient and cheaper than existing catalysts. This discovery in fuel cell research may ease reliance on gasoline. According to the researchers, the active phase of the catalyst consists of nanoparticles with a platinum-rich shell and a core made of an alloy of copper, cobalt, and platinum. But it's not enough for this new catalyst to be more efficient and cheaper than a pure platinum one. It also needs to work for a long time — say, the life of a car. So far, the preliminary results look promising, but longer-term testing is needed before this kind of fuel cells can be used to power your car."
Platinum is good at binding gas molecules to its surface (adsorbing them), which changes the nature of their electron clouds. This helps overcome the the van der Waals forces that hold them together or apart, making them more likely to react.
Nobody knows for certain just why platinum is good at adsorbing gas molecules to its surface.
In fact, fuel cells can run on other materials, e.g., methane, but this is typically done by the simple trick of using a reformer to produce hydrogen from the methane, and running that hydrogen in a fuel cell. And this can be difficult if the source of the methane is less than extremely pure; in that a lot of common impurities can poison either the catalyst or the reformer.
So, without a good means of storing hydrogen, it's not at all clear that advances in fuel cell technology are terribly useful.
Still, gotta start somewhere...
http://www.geoffreylandis.com
Even if this is a proven method, there's also a cost obstacle to overcome here. Platinum is already used in catalytic converters and those of us who, unfortunately, have a ULEV (Ultra Low Emission Vehicle) Honda Accord ought to know that their converter costs an arm and a leg. FYI: A retail catalytic converter for a ULEV car costs ~$1,800! (It has high platinum density) I managed to get an after market part for $650, and even then that's about twice what you would pay for a normal converter. The point is, there will be an even bigger premium for a hybrid with Platinum batteries. In the mean time, let's hope the gas prices get lower.
Some researchers at Purdue came up with a technique back in May that's probably better than this. It uses a Gallium/Aluminum alloy. Aluminum, when exposed to water, produces hydrogen and aluminum oxide. Normally aluminum produces an aluminum oxide layer immediately on any exposed surface, preventing further reaction. This alloy doesn't have that problem. It's unclear precisely how much platinum they require for this process from the news release, but Platinum is far more expensive than either Aluminum or Gallium. Another advantage is that the Gallium is unaffected and can be reused, while the aluminum oxide can readily be converted back to pure aluminum through Fused Salt Electrolysis. The cost of aluminum would make the cost of using this more than the equivalent of the current ~$3/gallon of gas. If there were enough demand and, using the recycling method, the cost of aluminum could be brought down to make it cheaper than the current cost of gas, however. Of course, electricity for the electrolysis has its own environmental impact...
The original journal articles for those interested in more than a press release:
Efficient Oxygen Reduction Fuel Cell Electrocatalysis on Voltammetrically Dealloyed Pt-Cu-Co Nanoparticles (Strasser et al., Angewandte Chemie International Edition)
http://dx.doi.org/10.1002/anie.200703331
Electrocatalysis on Bimetallic Surfaces: Modifying Catalytic Reactivity for Oxygen Reduction by Voltammetric Surface Dealloying (Koh & Strasser)
http://dx.doi.org/10.1021/ja0742784
To fully answer that question would take a whole course on organometallic chemistry to explain, but it has to do with the d-electron configuration of the platinum, (d8), which results in organometallic compounds which can be either square planar or octahedral. The ability to switch between these structures (and related oxidation states) allows for transitions and bonding between the states which allows for the creation of intermediates necessary for catalytic reactions. Bulk platinum (i.e. as a heterogeneous catalyst) also has d-electrons available at the metal surface which can form bonding and anti-bonding ( = bond breaking) bonds with small molecules. Essentially when it is reacting with, say, hydrogen gas, the H2 adsorbs onto the surface and, each atom forming a bond with one Pt atom's d-orbital.
A good book might be Heterogeneous Catalysts for the Synthetic Chemist (Google Book Search)
In addition to what's already been said, platinum is very resistant to being corroded even under very nasty conditions. Thus, it doesn't get used up in the process in which it's taking part.
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Disclaimer: IAAEVE. (I am an electric vehicle engineer.)
Fuel cells for the electricity will be even better.
Fuel cells will make sense the day we have so much renewable or other "clean" energy that we can afford to throw 80% of it away on the hopelessly inefficient Water electrolysis->Hydrogen->Fuel Cell cycle. Right now qualified renewables in the USA are some fraction of 1%. When do you anticipate we'll hit the 500% mark so that 4/5ths of it can be discarded to make hydrogen?
On the other hand, battery energy density is doubling every 8-10 years, meaning that battery EVs will have a 600-1000 km range within 2 decades -- enough driving for one day, even for the most car-addicted nation on the planet. Battery costs will benefit tremendously from economies of scale, but platinum (for your fuel cells) is not exactly going to get cheaper in quantity.
And don't go on about wind and solar - even maxed out they barely make a dent.
The available solar energy on Earth more than 5,000 times the total amount of energy used by all mankind. It's a pretty big dent. Oh, and wind energy is "only" 200 times.