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Researchers discover recipe for cheaper, more efficient fuel cell

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December 1, 2009

In a PEM fuel cell, the hydrogen is fed by a tank from (A); their electrons are extracted ...

In a PEM fuel cell, the hydrogen is fed by a tank from (A); their electrons are extracted and forced into (B), where their movement generates electricity; the parts later react with oxygen to form water, in part expelled (C) and in part used to cool the device.

Known mainly for their potential application in hydrogen cars, fuel cells are a promising technology with several unresolved issues, including working temperatures. Scientist at the University of Calgary have discovered a new material that allows a common kind of fuel cell to work at higher temperatures, increasing efficiency while decreasing manufacturing costs.

PEM fuel cells (and their issues)

A fuel cell is essentially a device that can produce electricity from externally supplied fuel without internal combustion, which allows for theoretically higher efficiency compared to traditional engines. The fuel is extracted from a tank and undergoes a chemical reaction that extracts electrons from it, then forcing them into a dedicated channel where their movement generates electricity.

Fuel cells can be used for a range of applications ranging from public transportation to radio controlled cars, as well as portable electronics such as laptops or mobile phones. They run on a number of different fuels including methanol and formic acid.

But in practice, when it comes to high power-density applications such as transportation, the choice for the fuel to be used is limited: extracting atoms from the fuel requires high energy levels, forcing us to choose hydrogen (because of its weak atomic bonding) over otherwise strong candidates like methane.

The cell that uses hydrogen to generate electricity is known as the proton exchange membrane fuel cell (PEMFC or simply PEM). In it, as explained above, the electrons are separated from the hydrogen molecules and travel through a circuit generating electricity; as the two components then reunite and react with oxygen, they then produce water, which is in part expelled as a waste product and part used to maintain the cell at an optimal temperature.

Currently, PEM cells can in fact produce energy only below 90 Celsius degrees, just under the boiling point of water, even though achieving higher temperatures would mean lower production costs: in fact, with these temperatures platinum needs to be used to separate hydrogen into its components; but with higher temperatures, less expensive materials could be employed to achieve the same effect.

There is, of course, also the specular issue of keeping the cell temperature above the freezing point of water, which might be a significant problem in certain regions of the globe. These and other issues are some of the reasons for the relatively reduced impact that PEM fuel cells have made in transportation. However, promising leads may mean we might be closer to solving these problems than we think.

Improving efficiency in PEM fuel cells

In a research paper published in a recent issue of Nature Chemistry, a team led by Prof. Shimizu at the University of Calgary explained how a new material could allow energy to be produced at higher temperatures — up to 150 degrees Celsius — therefore improving efficiency and reducing costs.

Using the material developed by the team will also make fuel cells more efficient because reactions would occur faster at those higher temperatures. "This research will alter the way researchers have to this point perceived candidate materials for fuel cell applications," Prof. Shimizu commented.

Kevin Colbow, director of research and development at hydrogen fuel cell manufacturer Ballard Power Systems, called the work significant. "We believe that further improvement on conductivity and robustness of these materials could provide next generation membranes for PEM fuel cells," he said.

We'll continue monitoring the progress of PEM fuel cell technology, especially as a promising second solution to similarly increase the working temperatures of fuel cells using polybenzimidazole — the material used in firefighter suits — has also recently surfaced.

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion.   All articles by Dario Borghino
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1 Comment

But what, pray tell, is the material? Inquiring minds want to know!

The answer is cunningly hidden in the abstract of the article, all 10 lines of it:

Metal organic frameworks (MOFs) are particularly exciting materials that couple porosity, diversity and crystallinity. But although they have been investigated for a wide range of applications, MOF chemistry focuses almost exclusively on properties intrinsic to the empty frameworks; the use of guest molecules to control functions has been essentially unexamined. Here we report Na3(2,4,6-trihydroxy-1,3,5-benzenetrisulfonate) (named β-PCMOF2), a MOF that conducts protons in regular one-dimensional pores lined with sulfonate groups. Proton conduction in β-PCMOF2 was modulated by the controlled loading of 1H-1,2,4-triazole (Tz) guests within the pores and reached 5 10-4 S cm-1 at 150 °C in anhydrous H2, as confirmed by electrical measurements in H2 and D2, and by solid-state NMR spectroscopy. To confirm its potential as a gas separator membrane, the partially loaded MOF (β-PCMOF2(Tz)0.45) was also incorporated into a H2/air membrane electrode assembly. The resulting membrane proved to be gas tight, and gave an open circuit voltage of 1.18 V at 100 °C.

Crazy Eddie
2nd December, 2009 @ 07:54 am PST
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