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Secrets of Ancient Egypt May Spark Better Fuel Cells for Tomorrow’s Cars
John Hopkins University
28/12/2017

To make modern-dayfuel cells less expensive and more powerful, a team led by Johns Hopkinschemical engineers has drawn inspiration from the ancient Egyptian tradition ofgilding.

Egyptian artists atthe time of King Tutankhamun often covered cheaper metals (copper, forinstance) with a thin layer of a gleaming precious metal such as gold to createextravagant masks and jewelry. In a modern-day twist, the Johns Hopkins-ledresearchers have applied a tiny coating of costly platinum just one nanometerthick-100,000 times thinner than a human hair—to a core of much cheaper cobalt.This microscopic marriage could become a crucial catalyst in new fuel cellsthat generate electric current for powering cars and other machines.

To improve fuel-cell technology, a team led by Johns Hopkins engineers took a cue from ancient Egyptian artists who who applied a thin coating of expensive gold over less expensive materials on creations like this death mask for King Tut. Image credit: Mary Harrsch/Flickr


The new fuel celldesign would save money because it would require far less platinum, a very rareand expensive metal that is commonly used as a catalyst in present-dayfuel-cell electric cars. The researchers, who published their work earlier say that by making electric cars more affordable, this innovation couldcurb the emission of carbon dioxide and other pollutants from gasoline- ordiesel-powered vehicles.


"This technique couldaccelerate our launch out of the fossil fuel era,” said Chao Wang, a JohnsHopkins assistant professor of chemical and biomolecular engineering and seniorauthor of the study. “It will not only reduce the cost of fuel cells. It willalso improve the energy efficiency and power performance of clean electricvehicles powered by hydrogen."

In his lab, ChaoWang, a Johns Hopkins assistant professor of chemical and biomolecularengineering, inspects a glass vial containing cobalt cores, each coated with athin layer of platinum. These materials help produce a cleaner and moreefficient fuel cell. At left is postdoctoral fellow Lei Wang, lead author ofthe related research article. Photo by Will Kirk/Johns Hopkins University.

In his lab, Chao Wang, a Johns Hopkins assistant professor of chemical and biomolecular engineering, inspects a glass vial containing cobalt cores, each coated with a thin layer of platinum. These materials help produce a cleaner and more efficient fuel cell. At left is postdoctoral fellow Lei Wang, lead author of the related research article. Photo by Will Kirk/Johns Hopkins University.


The platinumnanoparticles coating a core of cobalt led to superior results in testsconducted by the research team. Image is from the team’s paper, published inNano Letters.

In their journalarticle, the authors tipped their hats to the ancient Egyptian artisans whoused a similar plating technique to give copper masks and other metallic worksof art a lustrous final coat of silver or gold. "The idea," Wang said,"is toput a little bit of the precious treasure on top of the cheap stuff."

He pointed out thatplatinum, frequently used in jewelry, also is a critical material in modernindustry. It catalyzes essential reactions in activities ranging from petroleumprocessing and petrochemical synthesis to emission control in combustionvehicles, as well as being used in fuel cells. But, he said, platinum’s highcost and limited availability have made its use in clean energy technologieslargely impractical-until now.

"There's a lot morecobalt out there than platinum," said lead author and Johns Hopkinspost-doctoral fellow Lei Wang (not related to Chao Wang). "We’ve been able tosignificantly stretch the benefits of platinum by coating it over cobalt, andwe even managed to enhance the activity of platinum at the same time."

Earlier attempts toplate precious metals on non-precious materials were largely stymied bygalvanic replacement reactions-oxidation of the non-precious metal. In thisstudy, the team successfully suppressed such reactions by introducing carbonmonoxide, a gas molecule that strongly binds to cobalt, protecting it fromoxidation.

Not only did thecobalt-platinum nanoparticles reduce the usage of platinum; they performedalmost 10 times better than platinum alone. The researchers said this enhancedcatalytic activity resulted from both the maximized exposure of platinum atomson the surface and from interactions between the two metals. "The intimatecontact between cobalt and platinum gives rise to compressive strain," Lei Wangsaid. "It shortens the distance between platinum atoms and makes the chemicalreactions more feasible on the surface."

Because platinum andother rare metals play key roles in many industrial applications, theimplications of this work extend beyond fuel cells. Currently, the team isworking on adapting their technique to other precious metals and non-precioussubstrates. New developments will target further applications of such materialsin chemical conversions of hydrocarbons.

"Many reactions thatdepend on precious metal catalysts could be rendered cheaper and more effectiveby taking advantage of our technology, "Chao Wang said. "At a time when we arebecoming painfully aware of the limits of our non-renewable sources of energyand materials, this technique points us in a very welcome new direction"

The paper’s authorsalso include Yifan Liu and Michael Giroux, both PhD candidates in the JohnsHopkins University Department of Chemical and Biomolecular Engineering; ZhenhuaZeng and Jeffrey Greeley of Purdue University; Cheng Ma and Miaofang Chi of OakRidge National Laboratory; and Jian Jin of the Chinese Academy of Sciences.

The platinum nanoparticles coating a core of cobalt led to superior results in tests conducted by the research team. Image is from the team’s paper, published in Nano Letters.

The research wassupported by National Science Foundation grant DMR-1410175 and a Johns HopkinsUniversity Catalyst Award. The researchers have obtained a provisional patentcovering this technique through the Johns Hopkins Technology Ventures office.




 
 
 
 
 
 
 
 
 
 
 

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