AsianScientist (Feb. 28, 2020) – In a study published in the journal ACS Nano, a research group in South Korea has found that graphene can be used to protect copper against corrosion.
Copper has been essential to human technology and is used in virtually all electronic devices that require wiring. However, the surface of copper oxidizes over time, even under ambient conditions, ultimately leading to its corrosion.
One method for protecting metal surfaces from corrosion is by coating them with materials that do not interact with air. Graphene has been studied extensively as a candidate for anti-corrosive coatings, but the protective effect of graphene is thought to be short-lived, less than 24 hours. In fact, some studies show that after the initial protective period, graphene appears to increase the rate of copper corrosion.
To shed light on the peculiar nature of graphene seen in copper, a research team led by Professor Son Hyungbin at Chung-Ang University, South Korea, studied graphene islands on a copper substrate and analyzed the patterns of the metal’s corrosion.
Using techniques such as Raman spectroscopy, scanning electron microscopy and white light interferometry, the researchers performed a detailed observation of graphene-coated copper corrosion over a span of 30 days.
At first, the team detected corrosion developing at the edges of the graphene-coated copper sheet, resulting in the formation of copper oxide (Cu2O). At the same time, the splitting of water vapor occurred on the graphene coat, supplying oxygen for the oxidation process.
Owing to graphene’s effect on ambient water vapor, the protected portion of the copper substrate was more corroded than the unprotected portion. Over time, the formation of Cu2O underneath the graphene sheet dispersed the strain, creating a hybrid-like structure.
However, after 13 days of exposure to ambient conditions, the team discovered something new. They observed that that the corrosion had significantly slowed down where the hybrid of graphene and Cu2O layer had formed. Meanwhile, the unprotected copper continued to corrode at a consistent rate, until it had penetrated far deeper than the corrosion under the graphene shield.
These findings show that graphene in fact protects copper from deep, penetrating oxidation, unlike what previous studies had concluded.
“For nearly a decade, graphene’s anti-corrosive properties have been controversial, with many studies suggesting that graphene accelerates the oxidation of copper, resulting in its corrosion,” said Son.
“We have shown for the first time that the graphene-Cu2O hybrid structure, which forms over a long period, significantly slows down the oxidation of copper in the long term, as compared to bare copper.”
The article can be found at: Lee et al. (2019) Time Evolution Studies on Strain and Doping of Graphene Grown on a Copper Substrate Using Raman Spectroscopy.
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Source: Chung-Ang University; Photo: Pixabay.
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