Novel bi-metallic palladium-tungsten nano-alloy an efficient low-cost fuel cell catalyst; simple microwave synthesis
16 October 2014
Swedish and Chinese researchers have fashioned a novel nano-alloy composed of palladium nano-islands embedded in tungsten nanoparticles supported on ordered mesoporous carbon as an efficient fuel cell catalyst. In a paper in the journal Nature Communications, they reported that despite a very low percentage of noble metal (palladium:tungsten=1:8), the hybrid catalyst material exhibits a performance equal to commercial 60% platinum/Vulcan for the oxygen reduction reaction in a fuel cell.
The researchers attributed the high catalytic efficiency to the formation of small palladium islands embedded at the surface of the palladium–tungsten bimetallic nanoparticles, generating catalytic hotspots. The palladium islands are ~1 nm in diameter, and contain 10–20 palladium atoms that are segregated at the surface. The results, they said, may provide insight into the formation, stabilization and performance of bimetallic nanoparticles for catalytic reactions.
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| A schematic model of the unique morphology of the alloy. The Pd-islands (light-brown spheres) are embedded in an environment of tungsten (blue spheres). Oxygen is represented by red spheres, and hydrogen by white spheres. Source: Umeå University. Click to enlarge. |
Conventional fuel cells require efficient catalysts to drive the chemical reactions involved in the fuel cell. Historically, platinum and its alloys have frequently been used as anodic and cathodic catalysts in fuel cells, but the high cost of platinum, due to its low abundance, has motivated researchers to find efficient catalysts based on earth-abundant elements.
In our study we report a unique novel alloy with a palladium (Pd) and tungsten (W) ratio of only one to eight, which still has similar efficiency as a pure platinum catalyst. Considering the cost, it would be 40 times lower.
—Thomas Wågberg, Senior lecturer, Department of Physics, Umeå University
The explanation for the very high efficiency is the unique morphology of the alloy. It is neither a homogeneous alloy, nor a fully segregated two-phase system, but rather something in between.
By advanced experimental and theoretical investigations, the researchers show that the alloy is composed of metallic Pd-islands embedded in the Pd-W alloy. The size of the islands are about one nanometer in diameter and are composed of 10-20 atoms that are segregated to the surface. The unique environment around the Pd-islands give rise to special effects that all together turn the islands into highly efficient catalytic hot-spots for oxygen reduction.
To stabilize the nanoparticles in practical applications, they are anchored on ordered mesoporous carbon. The anchoring keeps the nanoparticles stable over a long period of time by hindering them from fusing together in the fuel cell tests.
The unique formation of the material is based on a synthesis method, which can be performed in an ordinary kitchen micro-wave oven purchased at the local supermarket. If we were not using argon as protective inert gas, it would be fully possible to synthesize this advanced catalyst in my own kitchen.
—Thomas Wågberg
Wågberg and his colleagues have recently received funding from the Kempe Foundation to buy a more advanced microwave oven, and will be able to run more advanced experiments to fine-tune some of the catalyst properties.
Resources
Guangzhi Hu, Florian Nitze, Eduardo Gracia-Espino, Jingyuan Ma, Hamid Reza Barzegar, Tiva Sharifi, Xueen Jia,Andrey Shchukarev, Lu Lu, Chuansheng Ma, Guang Yang, and Thomas Wågberg (2014) “Small palladium islands embedded in palladium-tungsten bimetallic nanoparticles form catalytic hot-spots for oxygen reduction,” Nature Communications (5). doi: 10.1038/NCOMMS6253
There seems to be little or no doubt that one way or another fuel cell cars can hit the same costs as ICE.
If fuel costs prove to be any sort of problem, and there is little indication that they will be, they can always be built in a PHEV configuration.
So there would be no need for extended fuel stops even in extended journeys, and the car would remain pollution free at point of use and have the characteristic low NVH of electric vehicles.
This would also avoid the need for away from home charge points, and minimise the need for hydrogen fuelling stations.
Posted by: Davemart | 16 October 2014 at 03:29 AM
Yes DM. Replacing the ICE in a PHEV with a small FC would be a smart solution.
Assuming that the on board batteries would be good enough for 50 to 60 Km, very little H2 would be required.
Buyers could/should be able to buy the size of battery pack (10 kWh to 40 kWh) to best suit their requirement.
Posted by: HarveyD | 16 October 2014 at 09:27 AM
Platinum is only one of the cost drivers. A cell may produce only 0.5 volts under load, so you need 400 of them just to make 200 volts. Each cell membrane plate costs, this has to be considered when projecting FCV costs.
Posted by: SJC | 16 October 2014 at 11:38 AM
@SJC:
The DOE costs of course take account of the issues you raise, and put costs as competitive with ICE in a few years even without platinum free catalysts, which obviously help even more.
Posted by: Davemart | 16 October 2014 at 12:09 PM
DOE projections are just that, projections. The DOE never massed produced a car in its life and never will. When the auto industry can mass produce 200,000 FC cars that sell for under $30,000, then we can take notice.
Posted by: SJC | 16 October 2014 at 12:13 PM
Yes and I too will take notice when a Tesla electric with 200 mile range comes in at less than 30 large.
Posted by: Mannstein | 21 October 2014 at 04:40 PM