Nanocarbon and Hypergolic Reactions

 

A new study was released in ACS Nano about nanocarbon. The research was inspired by rocket fuel ignition. Scientists have created a nanoporous carbon with the highest surface area ever reported.

Researchers have attempted to increase the porosity of carbon. The increase of porosity exposes more of material surface. A new technique for creation has provided a huge advancement. Carbon surface area can now reach 4800 m² per gram. This is approximately a football field packed into a teaspoon of material. 

Emmanuel Giannelis is senior author of the paper and a Walter R Reed professor in the department of material science and engineering. He reports, “ having more surface per mass is very important, but you can get to a point where there is no material left. It’s just air. So the challenge is how much of that porosity you can introduce and still have structure left behind, along with enough yield to do something practical with it.”

Giannelis began working with Nikolas Chalmpes. Chalmpes has been creating material using hypergolic reactions. These reactions occur spontaneously, when  certain chemicals are mixed and  a fast intense burst of energy is released.

Chalmpes is lead author of the study. He reports “ I was trying to understand how to harness and control these unexplored reactions for synthesizing, various carbon nanostructure and after adjusting various parameters, I discovered that we might be able to achieve ultra high porosity. Until then, these reactions had only been used in rocket and aircraft systems and deep space probes for propulsion and hydraulic power.”

To begin, scientists used sucrose and a template material. This helps shape the carbon into a complex form. When mixed with the proper chemicals, the hypergolic reaction begins. It forms carbon tubes with a large amount of reactive molecular rings that have five carbon atoms instead of the six rings found in most carbon.

Finally, the material is mixed with potassium hydroxide. This eats away the less stable nanostructures. It creates a complex network of tiny pores.

Giannelis reports, “ when you do this very fast reaction, it creates a perfect situation where the system cannot relax and go to its lowest energy state, which it would normally do. Because of the speed of hypergolic reactions, you can stretch the material in a metastable configuration that you cannot get from the slow heating of a normal reaction.”

Scientists on this project at Cornell teamed up with the national Center of Scientific Research, Demo Kristos, in Greece. The team showed that the nanoporous material can absorb carbon dioxide twice as fast as  traditional activated carbons. They can capture 99% of its total capacity in under two minutes. This is a very fast acting sorbent!

Chalmpes summarizes, “ This approach offers an alternative strategy for designing and synthesizing carbon based material suitable for sorbents, catalyst supports and active materials for super capacitors, particularly in applications requiring space efficiency. Furthermore, the unique experimental conditions of hypergolic reactions, provide another pathway for the design and synthesis of electro catalysts with enhanced properties.”