It turns out graphene has been deceiving us this whole time
For years, materials scientists have wondered how a metal-free material like graphene could be such a good catalyst. Well, now there’s an answer.
While the properties of graphene as an atom-thick form of carbon have shown themselves to bring enormous potential for plant electronics and as ultra-efficient water filters, its ability to act as a catalyst in fuel cells has always puzzled materials scientists.
Increasingly, graphene has been used as a replacement for expensive platinum in fuel cells where the material catalyses the oxygen reduction reaction (ORR) essential to turn chemical energy into electrical energy.
But because graphene isn’t naturally metallic, it really shouldn’t show catalytic activity when used as a cathode which led to a team of researchers from Rice University investigating why this is the case.
In a paper published to the journal Carbon, the team eventually discovered that trace quantities of manganese contamination from the original graphite or reactants actually hide within the graphene lattice.
When the graphene enters the right conditions – such as in a fuel cell – those minute metal bits activate the ORR.
The reason analysis was so far unable to discover this until now is because the contrast between carbon and manganese atoms is so slight that the tools used to analyse them weren’t sensitive enough.
Metal stowaways
So whereas X-ray diffraction and X-ray photoelectron spectroscopy couldn’t show the manganese, a tool called plasma mass spectrometry was able to show it loud and clear.
The team then subjected graphene samples to an acid wash revealing that after five or six washes, the manganese had disappeared and so with it its catalyst capabilities.
The results now mean that we have to question other so-called metal-free materials.
“Single-atom catalysts can hide among graphene, and their activity is profound,” said James Tour who led the research team.
“So what has sometimes been attributed to the graphene was really the single metal buried into the graphene surface. Graphene is good in its own right, but in these cases, it was being made to look even better by these single metal-atom stowaways.”
Despite this, there is an upside to the research as it could help researchers find insight into how ultrathin catalysts like graphene can be improved.
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Part 1
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https://www.google.com.ng/url?q=http://www.cyclingweekly.com/news/latest-news/junior-time-trial-champion-gabriel-evans-admits-epo-use-203450&sa=U&ved=2ahUKEwjflJjUsMnZAhXCDOwKHTm0AB8QFjALegQIAxAB&usg=AOvVaw2EBHx55iWH9K7aFTFov7xh
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