Metal-free catalyst outperforms platinum in fuel cell

Noble way to low-cost fuel cells, halogenated graphene may replace expensive platinum
A schematic representation for the edge expansions of XGnPs is seen in the top images. The bottom images contain ball-mill capsule containing the pristine graphite and stainless steel balls. Credit: UNIST

Researchers from South Korea, Case Western Reserve University and University of North Texas have discovered an inexpensive and easily produced catalyst that performs better than platinum in oxygen-reduction reactions.

The finding, detailed in Nature's Scientific Reports online today, is a step toward eliminating what industry regards as the largest obstacle to large-scale commercialization of .

Fuel cells can be more efficient than internal combustion engines, silent, and at least one type produces zero at the tail pipe. Car and bus manufacturers as well as makers of residential and small-business-sized generators have been testing and developing different forms of fuel cells for more than a decade but the high cost and insufficiencies of have been the Achilles heel.

"We made metal-free catalysts using an affordable and scalable process," said Liming Dai, the Kent Hale Smith Professor of and engineering at Case Western Reserve and one of the report's authors. "The catalysts are more stable than platinum catalysts and tolerate and methanol crossover."

And, in their initial tests, a cathode coated with one form of catalyst—graphene nanoparticles edged with iodine—proved more efficient in the oxygen reduction reaction, generating 33 percent more current than a commercial cathode coated with platinum generated.

The research was led by Jong-Beom Baek, director of the Interdisciplinary School of Green Energy/Low-Dimensional Center at South Korea's Ulsan National Institute of Science and Technology. Fellow authors include: In-Yup Jeon, Hyun-Jung Choi, Min Choi, Jeong-Min Seo, Sun-Min Jung, Min-Jung Kim and Neojung Park, from Ulsan; Sheng Zhang from Case Western Reserve; and Lipeng Zhang and Zhenhai Xia from North Texas.

Like a battery, a converts chemical energy into electrical energy. It works by removing an electron from a fuel, usually hydrogen or methanol mixed with water, at the cell's anode, or positive electrode, creating a current.

Hydrogen ions produced then pass through a membrane to the cathode, or negative electrode. Here, oxygen molecules from the air are split and reduced by the addition of electrons and combined with the hydrogen ions to form water and heat—the only byproducts.

A better, cheaper catalyst than scarce and costly platinum is required if hydrogen fuel cells and direct methanol fuel cells are to become realistic alternatives to fossil fuels, the authors say.

The technology to make alternative catalysts builds on a simple and cheap industrial process several of the researchers developed to make graphene sheets from graphite.

Inside a ball miller, which is a canister filled with steel balls, the researchers broke graphite down into single-layer graphene nanoparticles. While the canister turned, they injected chlorine, bromine or iodine gas to produce different catalysts.

In each case, gas molecules replaced carbon atoms along the zigzag edges of nanoplatelets created by milling. Not only were the edges then favorable to binding with oxygen molecules, but the bond strength between the two oxygen atoms weakened. The weaker the oxygen bonds became, the more efficiently the oxygen was reduced and converted to water at the cathode.

In testing, a cathode coated with iodine-edged nanoplatelets performed best. A cathode coated with bromine-edged nanoparticles generated 7 percent less current than the commercial cathode coated with platinum, the chlorine-edged nanoplatelets 40 percent less.

In a test of durability, electrodes coated with the nanoplatelets maintained 85.6 percent to 87.4 percent of their initial current after 10,000 cycles while the platinum electrodes maintained only 62.5 percent.

Carbon monoxide was added to replicate the poisoning that many scientists blame for the poor performance of platinum at the cathode. The performance of the graphene-based catalysts was unaffected.

When methanol was added to replicate methanol crossover from the anode to cathode in direct methanol fuel cells, the current density of the platinum catalyst dropped sharply. Again, the graphene-based catalysts were unaffected.

"This initial research proves such catalysts work better than ," Baek said. "We are working now to optimize the materials."

Explore further

As fuel cells evolve, a role emerges for palladium

More information: Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free electrocatalysts for oxygen reduction reaction, Scientific Reports, DOI: 10.1038/srep01810
Journal information: Scientific Reports

Citation: Metal-free catalyst outperforms platinum in fuel cell (2013, June 5) retrieved 14 October 2019 from
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Jun 05, 2013
They're making little molecular doilies!

Jun 05, 2013
This could be a major breakthrough in fuel cells and catalysts in general. If all of this is really true fuel cells could finally come of age and become a cost efficient way to produce power.

Jun 05, 2013
Holy moly, where and when do they go on sale.

My thoughts exactly. Those last three paragraphs seem to be the understatement of the year.

With the sulfur-lithium and sodium(or zinc)/air batteries poised to take over from lithium-ion types it looks like we now have the tech for replacing fossil fuels in personal transport (batteries) and commercial transport (fuel cells).

...and possibly even in the greatest polluter of all: shipping.

Man, the tech just explodes in these areas in the last few years. It seems the decades of research there are really paying off.

Jun 05, 2013
Direct link to the above report.

Jun 05, 2013
There is no doubt that cheap power storage would transform society for the better.

Jun 06, 2013
Contemporary Luddites hate when green boondoggles actually work!

Jun 08, 2013
"How useful?" . This one fails on 3
The research in contemporary science is mostly driven with its usefulness for research community, not for people, who are paying it. From the same reason the otherwise interesting nuclear effects of cold fusion aren't studied - it would compete the research of all alternative methods of energy production/conversion/transport and storage, which provide jobs and salaries for many scientists involved. Such a trend could be easily modeled mathematically: if we put the money blindly into some community of people, soon or later this community will adjust the rules of its existence and work in just the way, which will serve its income, not the results.

Jun 08, 2013
The interesting part of this paper seems to be the fact the catalyst is metal free (presumably cheap to manufacture) and is not poisoned by CO (unlike Pt).

I think it is worth pointing out this work was performed in an alkaline electrolyte, and some challenges still remain in the development of alkaline membranes (whereas Pt loaded PEM fuel cells typically use the acidic NAFION membrane).

Also, I find the statement "And, in their initial tests, a cathode coated with one form of catalyst—graphene nanoparticles edged with iodine—proved more efficient in the oxygen reduction reaction, generating 33 percent more current than a commercial cathode coated with platinum generated." highly misleading. It is completely meaningless to discuss efficiency without reference to the cell potential where the current is compared. For example, from figure 3f in the manuscript it is seen there are potentials where the Pt catalyst produce about 500 percent more current than the graphene based catalysts.

Jun 09, 2013
When evaluating claims of new breakthrough "techniques", I usually ask 1) "How effective if it works as claimed?", 2) "How producible?", and 3) "How useful?" . This one fails on 3), since fuel cells depend on a fuel, and that amounts to either a) pure hydrogen (difficult and expensive) or b) a carbohydrate (fossil increasingly rare and artificial difficult to produce). What everyone fails to grasp is that, in the long term (100+ years) this is essentially a political problem. We might overcome this if we made a tremendous effort to replace all our energy uses with solar power (see Desertec), but present political organization will not allow this to start in time to enable any effective conclusion. If we don;t change our political organization, no technical solution can suffice.

1. They tested their new catalyst with methanol, an alcohol made from cellulose.
2. Methanol eliminates the need for pure hydrogen.
3. Fossil fuels are hydrocarbons, not carbohydrates.

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