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Laser-burned graphene gains metallic powers

Scientists find possible replacement for platinum as catalyst

Date:
August 20, 2015
Source:
Rice University
Summary:
Chemists embed metallic nanoparticles into laser-induced graphene, turning it into a useful catalyst for fuel cell and other applications.
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A scanning electron microscope image shows cobalt-infused metal oxide-laser induced graphene produced at Rice University. The material may be a suitable substitute for platinum or other expensive metals as catalysts for fuel cells. The scale bar equals 10 microns.
Credit: Tour Group/Rice University

Rice University chemists who developed a unique form of graphene have found a way to embed metallic nanoparticles that turn the material into a useful catalyst for fuel cells and other applications.

Laser-induced graphene, created by the Rice lab of chemist James Tour last year, is a flexible film with a surface of porous graphene made by exposing a common plastic known as polyimide to a commercial laser-scribing beam. The researchers have now found a way to enhance the product with reactive metals.

The research appears this month in the American Chemical Society journal ACS Nano.

With the discovery, the material that the researchers call "metal oxide-laser induced graphene" (MO-LIG) becomes a new candidate to replace expensive metals like platinum in catalytic fuel-cell applications in which oxygen and hydrogen are converted to water and electricity.

"The wonderful thing about this process is that we can use commercial polymers, with simple inexpensive metal salts added," Tour said. "We then subject them to the commercial laser scriber, which generates metal nanoparticles embedded in graphene. So much of the chemistry is done by the laser, which generates graphene in the open air at room temperature.

"These composites, which have less than 1 percent metal, respond as 'super catalysts' for fuel-cell applications. Other methods to do this take far more steps and require expensive metals and expensive carbon precursors."

Initially, the researchers made laser-induced graphene with commercially available polyimide sheets. Later, they infused liquid polyimide with boron to produce laser-induced graphene with a greatly increased capacity to store an electrical charge, which made it an effective supercapacitor.

For the latest iteration, they mixed the liquid and one of three concentrations containing cobalt, iron or molybdenum metal salts. After condensing each mixture into a film, they treated it with an infrared laser and then heated it in argon gas for half an hour at 750 degrees Celsius.

That process produced robust MO-LIGs with metallic, 10-nanometer particles spread evenly through the graphene. Tests showed their ability to catalyze oxygen reduction, an essential chemical reaction in fuel cells. Further doping of the material with sulfur allowed for hydrogen evolution, another catalytic process that converts water into hydrogen, Tour said.

"Remarkably, simple treatment of the graphene-molybdenum oxides with sulfur, which converted the metal oxides to metal sulfides, afforded a hydrogen evolution reaction catalyst, underscoring the broad utility of this approach," he said.

The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research.


Story Source:

Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.


Journal Reference:

  1. Ruquan Ye, Zhiwei Peng, Tuo Wang, Yunong Xu, Jibo Zhang, Yilun Li, Lizanne G. Nilewski, Jian Lin, James M. Tour. In situFormation of Metal Oxide Nanocrystals Embedded in Laser-Induced Graphene. ACS Nano, 2015; 150818130933000 DOI: 10.1021/acsnano.5b04138

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Rice University. "Laser-burned graphene gains metallic powers: Scientists find possible replacement for platinum as catalyst." ScienceDaily. ScienceDaily, 20 August 2015. <www.sciencedaily.com/releases/2015/08/150820134713.htm>.
Rice University. (2015, August 20). Laser-burned graphene gains metallic powers: Scientists find possible replacement for platinum as catalyst. ScienceDaily. Retrieved May 26, 2017 from www.sciencedaily.com/releases/2015/08/150820134713.htm
Rice University. "Laser-burned graphene gains metallic powers: Scientists find possible replacement for platinum as catalyst." ScienceDaily. www.sciencedaily.com/releases/2015/08/150820134713.htm (accessed May 26, 2017).

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