Graphene may find future in copper baths

Researchers in Europe have been experimenting with liquid copper in graphene production and have postulated a faster and cheaper method to reliably produce this miracle material.

Together with experimental partners from the Netherlands, France, and Greece, researchers from the Technical University of Munich, as part of a European project called LMCat (liquid metal catalysis), aim to unravel the growth mechanism of graphene on liquid copper by combining experiments and computer simulations.

According to the Gauss Centre for Supercomputing, liquid copper has taken the stage as an exciting catalyst for fast and efficient industrial-scale production of high-quality graphene. However, current knowledge regarding the catalytic properties of liquid metal catalysts is severely lacking, as studying such principles has had no technological significance in the past.

In a recent research highlights article, Gauss Centre for Supercomputing author Eric Gedenk provided a window into the center's efforts to develop a method to reliably produce high-quality graphene cheaper and faster.

To address the challenge of producing graphene in large volumes, the team at the Technical University of Munich has been using JUWELS (Jülich Wizzard for European Leadership Science) and SuperMUC-NG, high-performance computing systems, at the Jülich Supercomputing Center and Leibniz Supercomputing Center to run high-resolution simulations of graphene formation on liquid copper.

The reason scientists are bringing supercomputing into the mix is, we know little about the molecular interactions happening during the brief, chaotic moments that lead to graphene formation.

So how does copper fit into the equation?

Firstly, graphene is considered an allotrope (same element, different form) of carbon – it is essentially the same as graphite but with a different atomic structure.

As it is only one atom thick – classifying it as a two-dimensional material – it has provided untold headaches in creating large quantities for manufacturing or even research purposes.

The initial method of deriving graphene was using the famed "scotch tape" method, which won the Nobel prize in 2010 for physics. This technique, however, is too cumbersome and time-consuming as you use actual tape to slowly whittle away the layers of graphite until you are left with a single atomic layer.

Liquid copper has the potential to change this method by providing a "bath" of atoms that allow the carbon molecules to fall into place on their own.

Conversely, challenges have arisen from even simulating the process using supercomputers as the behavior of a dynamic system such as liquid is not without its own set of complications.

"The problem describing anything like this is you need to apply molecular dynamics simulations to get the right sampling," said Mie Andersen, co-author of the work detailing graphene growth on liquid copper. "Then, of course, there is the system size – you need to have a large enough system to accurately simulate the behavior of the liquid."

Unlike physical experimentation, molecular dynamics (MD) simulations offer researchers the ability to look at events happening on the atomic scale with complete control of the simulation.

While this sounds reasonable, the resources required to simulate MD have been colossal, which has been another challenge the team has had to face.

Despite a massive computational effort that involved roughly 2,500 cores on JUWELS, each equivalent to a core on your home computer, after more than a month the team could only simulate around 1,500 atoms over picoseconds of time.

Although current-generation supercomputers have enabled the team to run its simulations, this is trailblazing research as little study has been able to be undertaken before mankind had processing powers such as JUWELS and SuperMUC-NG.

The team published its record-breaking simulation work in the "Journal of Chemical Physics", then used those simulations to compare with experimental data obtained in their most recent paper, which appeared in "ACS Nano".

As humankind learns more about the functions and principles of the infinitesimally small spheres that define and make up the physical universe, it is evident that new and exciting technologies such as growing graphene in liquid copper will be just the beginning of even more wondrous discoveries.