New nanoparticle catalyst brings fuel-cell cars closer to showroom

March 19, 2008
New nanoparticle catalyst brings fuel-cell cars closer to showroom
UW-Madison and University of Maryland researchers developed a new type of catalyst by surrounding a nanoparticle of ruthenium with one to two layers of platinum atoms. The result is a robust room-temperature catalyst that dramatically improves a key hydrogen purification reaction and leaves more hydrogen available to make energy in the fuel cell. Credit: University of Wisconsin-Madison

A University of Wisconsin-Madison and University of Maryland (UM) team has developed a new nanotechnology-driven chemical catalyst that paves the way for more efficient hydrogen fuel-cell vehicles.

Writing in this week's Advance Online Publication of Nature Materials, UW-Madison chemical and biological engineering Professor Manos Mavrikakis and UM chemistry and biochemistry Professor Bryan Eichhorn describe a new type of catalyst created by surrounding a nanoparticle of ruthenium (Ru) with one to two layers of platinum (Pt) atoms. The result is a robust room-temperature catalyst that dramatically improves a key hydrogen purification reaction and leaves more hydrogen available to make energy in the fuel cell.

One day, it could be common for fuel cells to create electricity by consuming hydrogen generated from renewable resources. For now, most of the world's hydrogen supply is derived from fossil fuels in a process called reforming.

An important step in this multistage process, called preferential oxidation of CO in the presence of hydrogen (PROX), uses a catalyst to purge hydrogen of carbon monoxide (CO) before it enters the fuel cell. CO presents a major obstacle to the practical application of fuel cells because it poisons the expensive platinum catalyst that runs the fuel cell reaction.

Attractive for transportation applications and as a battery replacement, proton exchange membrane fuel cells generate electricity using porous carbon electrodes containing a platinum catalyst separated by a solid polymer. Hydrogen fuel enters one side of the cell and oxygen enters on the opposite side. Platinum facilitates the production of protons from molecular hydrogen, and these protons cross the membrane to react with oxygen on the other side. The result is electricity with water and heat as byproducts.

A conventionally constructed catalyst combining ruthenium and platinum must be heated to 70 degrees Celsius or 158 degrees Fahrenheit in order to drive the PROX reaction, but the same elements combined as core-shell nanoparticles operate at room temperature. The lower the temperature at which catalyst activates the reactants and makes the products, the more energy is saved.

"We understand why it works," Mavrikakis says. "We know now the reason behind this marvelous behavior. The first reason is the core-cell nanostructure. This polymer-based method developed by my colleagues in Maryland allows the exact amount of an element, in this case platinum, to be placed exactly where you want it to be on specific seeds of ruthenium."

This very specific nano-architecture and composition can sustain significantly less CO on its surface than pure Pt would. Because the binding is weaker, Mavrikakis says fewer sites on the core-cell nanostructure are available to bind with CO than would occur with Pt alone. That leaves empty sites for oxygen to come in and react.

"The second reason is that there is a completely new reaction mechanism that makes this work so well," he says. "We call it hydrogen-assisted CO oxidation. It uses atomic hydrogen to attack molecular oxygen and make a hydroperoxy intermediate, which in turn, easily produces atomic oxygen. Then, atomic oxygen selectively attacks CO to produce CO2, leaving much more molecular hydrogen free to be fed to the fuel cell than pure Pt does."

While the breakthrough is important to the development of fuel-cell technology, the researchers say it's even more significant to catalysis in general.

First, the team, including graduate students Anand Nilekar of UW-Madison and Selim Alayoglu of Maryland, used theory rather than an experimental approach to zero in on ruthenium/platinum as the ideal core shell system.

Second, the nanoscale fabrication of ruthenium and platinum resulted in a different nano-architecture than when ruthenium and platinum are combined in bulk. For the field of catalysis, the pairing of these approaches could bridge the gap between surface science and catalysis opening new paths to novel and more energy-efficient materials discovery for a variety of industrially important chemical processes.

Source: University of Wisconsin-Madison

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googleplex
4 / 5 (1) Mar 19, 2008
Anyone seen the price of platinum lately?
Whilst the research process used is novel and exciting we won't see this used for a while.
This does not break our dependence on fossil fuels as the article clearly states.
Solar is the most effective way once the hydrocarbon "solar battery" has been used up.
Of course the white elephant fusion projects might one day work but i would not bet my life on it.
photonica
3 / 5 (1) Mar 20, 2008
googleplex is spot on.
Soylent
3 / 5 (1) Mar 20, 2008
"Solar is the most effective way once the hydrocarbon "solar battery" has been used up.
Of course the white elephant fusion projects might one day work but i would not bet my life on it."

Laughable. Solar is intermittent, low capacity factor, outrageously expensive, utterly incapable of providing base-load without peak power plant backup or batteries or HVDC lines spanning the globe.

Thankfully it looks like even politicians understand that solar isn't going to come to the rescue and are now hurrying to build fission reactors.
axemaster
5 / 5 (1) Mar 20, 2008
"Laughable. Solar is intermittent, low capacity factor, outrageously expensive, utterly incapable of providing base-load without peak power plant backup or batteries or HVDC lines spanning the globe."

Ever heard of high tension power lines? Those are HVAC.

But more importantly, the most useful aspect of solar energy isn't it's output. It's the fact that it is the first real non-centralized source of energy. What I mean is, it's far more efficient if everybody produces some of their own energy, and that they be hooked up to a smart powergrid. That smart powergrid automatically redistributes energy to places where it might be cloudy, ensuring that power remains every bit as continuous as with centralized power. Moreover, the system is self-upgrading, in the sense that people will always want the best product. The system cannot wear out, which eliminates one of the biggest criticisms of our current network - the same flaws that led to the NE blackout a few years ago.

It should be relatively obvious that it's easier for everybody to have, say, 4 panels, than for a power station to be built with 1,000,000 of them. It takes less time, will be better maintained, and, if you're a "defense person", would be almost invulnerable to any attack short of EMP. Analogy: think of the Internet. It's a distributed network, with thousands of servers performing small bits of work. Now imagine if they were all consolidated into 5 giant computers. Nothing would ever work - the system would crash constantly and would be impossible to maintain - that's what we have right now.

There are two reasons solar is so expensive right now - lack of research funding (compared to biofuel - utterly useless junk that it is), and lack of subsidization. If the government was really serious about getting solar on it's feet, they would increase the subsidies, which would then serve to jump-start the industry as customers flooded in. The rush of money would attract more researchers into the field, and bam! solar would advance technologically.

Distributed power is the way. Once one spreads out the system, everything starts to make a ton of sense.

-Axemaster
Soylent
not rated yet Mar 20, 2008
"Ever heard of high tension power lines? Those are HVAC."

Ever hear of parasitic losses due to capacitive coupling, corona discharge or asynchronous grids?

Only HVDC makes sense for distribution over such long distances and across differences in standards.

"That smart powergrid automatically redistributes energy to places where it might be cloudy, ensuring that power remains every bit as continuous as with centralized power."

If you want to go that route you need to build HVDC lines spanning across entire continents. And that's still not enough, you're going to have to overbuild by quite some margin to deal with seasonal variations.

"Moreover, the system is self-upgrading, in the sense that people will always want the best product."

How does this differ from any other type of generation? Are you suggesting that you have to force the utillities to construct new power plants?

"The system cannot wear out, which eliminates one of the biggest criticisms of our current network - the same flaws that led to the NE blackout a few years ago."

That may be your intention but it has the opposite effect. You want to distribute power generation, but giving everyone and their dog a couple of solar cells doesn't actually do this at all.

There's a very high correlation between the power output of solar cells in fairly large regions(due to seasonal variations, same time-zone, same weather). This makes your "distributed" power source equal to a single very flakey power station. The small number of thousands of miles long HVDC lines you're going to need to mitigate intermittency and make sure that at least some of the power provided by solar can be relied upon will further centralize power distribution; exactly the problem you sought to avoid. If parts of the HVDC network goes down you can experience continent wide problems instead of just a little local trouble.

"It should be relatively obvious that it's easier for everybody to have, say, 4 panels, than for a power station to be built with 1,000,000 of them."

It should be relatively obvious that the intermittent, very low capacity factor power generated by solar PV is a liabillity as far as the electric grid is concerned rather than an asset. You're just exporting the intermittency to the utillities. They will react by burning more expensive natural gas to handle the swings in load or generating more power than they really need through coal or nuclear to make sure they have overcapacity. That's not very helpful.

"It takes less time, will be better maintained, and, if you're a "defense person", would be almost invulnerable to any attack short of EMP."

Unfortunately, you'll be more vulnerable to dependency on dwindling natural gas supplies, dependency on a smaller number of vital power lines and freak weather.

"There are two reasons solar is so expensive right now - lack of research funding (compared to biofuel - utterly useless junk that it is)..."

There's a good reason for that. Bio-fuels could at least have some use; but without a miraculous breakthrough in power distribution or energy storage or at least some kind of worthwhile use for cheap intermittent power solar PV is not useful. Even if solar cells are free, there's a very significant cost associated with using the power they produce.

"...and lack of subsidization."

Wind and solar are very highly subsidized. See for instance net metering(i.e. forcing utilities to pay full price, including the cost of distribution on their own lines, for near useless intermittent power), large tax deductions and various other incentives.
RealScience
not rated yet Mar 21, 2008
Let's clear up some misconceptions:

axemaster: distributed solar is more expensive than concentrated; PER PANEL it costs more to mount solar panels on roofs than at a solar farm, and solar farms can be in ultra-sunny desert and avoid partial shading, etc., and hence produce more power, too. Individual solar also still requires a grid for backup (batteries are expensive and very eco-unfriendly per amount of storage). Individual solar does have three roles: 1) people can do something to kick-start the industry, and 2) building-integrated PV is
starting to become cost effective for new construction, and 3) solar hot water can very cost-effectively displace electricity that would have gone to heating water. But if you really want to save the world, don't fight the electric utilities - encourage them to make billions from solar when its price is finally competitive.

soylent: the initial argument was about solar for hydrogen; if one converts to hydrogen one needs pipelines, not HVDC transmission lines, to transport the energy, and one stores it as hydrogen as well. And HVDC works very well, bringing huge amounts of power from Northern Quebec to southern Quebec, New York and New England.

axemaster: to the un-trained eye, HVDC power lines look a lot like HVAC power lines. And soylent is right, we will need more of them.

gooxplex photonica: Pure hydrogen is a joke regardless. Hydrogen is not an energy source, it is an energy storage medium, and not a very good one at that. We should converting solar hydrogen to methanol or ethanol, not hydrogen, and work on improving direct methanol or ethanol fuel cells. Or if solar is cheap enough, just get rid of the one oxygen and get naturalk gas, propane, hexane (gasoline), diesel, etc. We already have the infrastructure for these, so soylent's transportation and storage arguments go away. If you want to be super-green, pull the carbon from the air to make these fuels...

soylent: Solar is indeed too expensive today, but no longer "outrageously" so. The electric power peak demand roughly coincides with the solar peak; in high-sun areas solar is already roughly at parity for cherry-picking this peak, which covers tens of gigaWatts. After that, solar is nicely complementary to hydro-electric generation; simply hold back the water when solar exceeds demand, and release the water once solar falls short of demand.

soylent: biofuel from food (or on land where it displaces food production) is ridiculous - far more environmentally destructive even than strip-mined coal. Only when biofuel is made from what would be waste it is a net environmental benefit.

soylent: Solar can even go beyond peak-power and current hydropower for intermittency, and it won't require "a miraculous breakthrough in power distribution or energy storage". Pumped-hydro storage scales very well and has a long track record (Storm King dates back at least to the 1960s), so the real issue is only the price of solar power. While solar is indeed several times too expensive for this today, costs have been falling steadily, and all it takes is 15 more years of continued progress for solar to reach parity in the U.S. That's centralized solar in sunny areas, and includes storage losses and also transmission losses to reach the east coast.

subsidy lovers: Yes, massive subsidies of solar would make solar installations happen faster, but they wouldn't force true costs down fast enough. Simply make nuclear pay for its own (past) development, current liabilities and waste storage; have oil and gasoline pay for the Iraq war and have all fossil fuels pay for their own environmental damage; stop subsidizing destructive food and food-displacing biofuels, and then let nature take its course. In a few decades we%u2019ll probably end up with 10% hydro, 15% wind, 50% solar, and 25% miscellaneous (waste-based biofuels, still-running nuclear, tidal, natural gas, carbon-capture coal, etc.). But if each pays for its own sins, who cares which one wins? We win regardless!
COCO
not rated yet Mar 25, 2008
we pay anyone $.20 a KW for solar ( in Ontario Canada) yet solar remains a toy with petulant fans but no eco impact.
googleplex
not rated yet Apr 04, 2008
Solar is distributed. Saves costs.
It is free and clean. Saves costs.
It is an add on to already existing electric infrastructure.
You feed surplus solar back into the existing power grid.
Peak usage is during peak sunlight hours.
Easy DC - AC conversion using existing inverters.
Most electronics in the home are DC powered.
Do away with inefficient transformers.
DC is safer in the home.
If you want old fashioned large power plants, then put reflective foils in space to beam solar radiation to surface in a concentrated area.

True it is not cost effective today.
However solar obeys Moores law in terms of cost per watt so it will get there. In addition if oil goes up 25% a year then the cross over point will arrive sooner.
Lead acid batteries are used to store power locally, cheap and very efficient.
Thin flexible film solar will reduce installation costs.
If you look at the raw efficiency solar is the way to go long term.
Bio fuels are bunk. They are too expensive to distribute, and would require enormous infrastructure capital cost. Enivornmentally unfriendly.
Fossil fuels will run out one day.

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