Scientists from Skoltech, MIPT, the RAS Institute of Solid State Physics, Aalto University and other institutions have proposed the first carbon monoxide-based graphene synthesis technique. It is a simple and quick way to make high-quality graphene for use in gas sensors, electronic circuits, optics and other applications.
Snowflakes etched in graphene at Skoltech. The light areas are graphene, and the dark ones are oxidized copper. The snowflake pattern emerged as the surrounding graphene was etched away by carbon dioxide in one of the experiments before the optimal gas composition was found. Image Credit: Artem Grebenko/Skoltech
The research was published in the esteemed journal Advanced Science.
Chemical vapor deposition is the industry standard for producing graphene, a one-atom-thick sheet of carbon atoms arranged in a honeycomb pattern with unrivaled properties useful for electronics and other applications. Carbon atoms break off gas molecules and settle as a monolayer on a substrate in a vacuum chamber during CVD.
Copper has long been a popular substrate, and the gases used have always been hydrocarbons—propane, methane, spirits, acetylene, and so on.
The idea to synthesize graphene from carbon monoxide came a long time ago, since that gas is one of the most convenient carbon sources for the growth of single-walled carbon nanotubes. We have had working experience with carbon monoxide for almost 20 years.
Albert Nasibulin, Study Principal Investigator and Professor, Skoltech
Albert Nasibulin adds, “However, our first experiments with graphene were unsuccessful, and it took us a long time to understand how to control the nucleation and growth of graphene. The beauty of carbon monoxide is in its exclusively catalytic decomposition, which allowed us to implement self-limiting synthesis of large crystals of single-layer graphene even at ambient pressure.”
This project is one of the brilliant examples of how fundamental studies benefit applied technologies. The optimized conditions leading to the formation of large graphene crystals became feasible owing to an understanding of the deep kinetic mechanism for graphene formation and growth verified by both theory and experiment.
Dmitry Krasnikov, Study Co-Author and Senior Research Scientist, Skoltech
The new technique takes advantage of the so-called self-limiting principle. When carbon monoxide molecules come into close proximity with the copper substrate at high temperatures, they break up into oxygen and carbon atoms. This tendency fades after the first layer of crystalline carbon is deposited and separates the gas from the substrate.
The process naturally favors the formation of a monolayer. Methane-based CVD can also be self-limiting, but only to a limited extent.
Artem Grebenko, the study’s first author and Skoltech intern adds, “The system we used has a number of advantages: The resulting graphene is purer, grows faster, and forms better crystals. Moreover, this tweak prevents accidents with hydrogen and other explosive gases by eliminating them from the process altogether.”
As the method eliminates the risk of combustion, no vacuum is needed. The device operates at standard pressure, making it much easier to use than traditional CVD equipment. As a result of the simplified design, synthesis is faster. Grebenko remarks, “It only takes 30 minutes from taking a bare piece of copper to pulling out the graphene.”
Since the vacuum is no longer required, the equipment not only works faster but is also less expensive. “Once you drop the high-end hardware for generating ultrahigh vacuum, you can actually assemble our ‘garage solution’ for no more than $1,000,” the researcher adds.
Boris Gorshunov, Study co-author and a professor at MIPT, emphasized the high quality of the resulting material.
Whenever a new graphene synthesis technique is presented, it is imperative that the researchers prove that it produces what they claim it does. After rigorous testing, we can say with confidence that ours is indeed high-grade graphene that can compete with the material produced via CVD from other gases. The resulting material is crystalline, pure, and comes in pieces large enough to be used in electronics.
Boris Gorshunov, Study Co-Author and Professor, Moscow Institute of Physics and Technology
Apart from the standard graphene applications, there are some interesting possibilities for using graphene bound to a copper substrate—without having to remove the metal. Carbon monoxide does have very high energy of adhesion to metal when compared to methane.
As graphene is deposited, it safeguards the copper layer from chemical reactions while also providing structure, resulting in a relatively sophisticated metal surface with excellent catalytic properties. Other metals, such as ruthenium and palladium, could also be used to create novel materials with unusual surfaces in this context.
In addition to Skoltech, MIPT, ISSP RAS and Aalto, the research included scientists from HSE University, Dukhov Research Institute of Automatics, Donostia International Physics Center, NUST MISIS, FU Berlin, IFW Dresden, Swiss Federal Laboratories for Materials Science and Technology, Boreskov Institute of Catalysis, MEPhI and Rutgers University.
The work carried out on the BESSY II light source at HZB Berlin was vital for the research, and Skoltech scientists also acknowledge the same.
Journal Reference:
Grebenko, A. K., et al. (2022) High-Quality Graphene Using Boudouard Reaction. Advanced Science. doi.org/10.1002/advs.202200217.