With YME Pecha Kucha being held last Sunday (the content of which can be read in the adjacent article for today, right here at YME Insider), we have decided to pick one of the topics discussed by the speakers and delve into a tangential line of thinking. Hence, we have decided to go with the final speaker, Mr. Prabhuraj Balakrishnan, who talked about methanol fuel cells aided by graphene. Admittedly, the writer understands little about the actual design of the fuel cell and, with it being patent-protected, there wouldn’t be much of a point to it anyway. Hence, we shall explore this wonderful material graphene and how it works.

First Contact

Figure 1: Graphene Stripped From Graphite

Firstly, let’s look into what graphene actually is. Every STEM student worth their salt should know by now that graphene is a single layer of carbon atoms arranged in a hexagonal sheet. Chemically, this form of carbon is a stable configuration that could, in theory, exist in the natural world. However, carbon closest to this configuration (also called an allotrope of carbon) that exists in the natural world is graphite, which is basically multiple graphene layers stacked on top of each other. Graphite should sound quite familiar as it is the very material that makes up pencil lead.

The history of graphene is similarly interesting. It was all the way back in 1962 that this material was observed (admittedly, only while supported on metal surfaces and not independently) in electron microscopes. Flash forward to 2004, graphene was rediscovered, isolated and characterized by the esteemed scientists Andre Geim and Konstantin Novoselov at the University of Manchester (which also saw the birth of YME-UK and YME Insider, proving that great discoveries and creations usually come from similar geographical locations). Famously, these physicists synthesized graphene using a technique derived from Scotch tape. Having studied how the single-layer carbon configuration can be achieved by using a strip of Scotch tape that is repeatedly folded around some graphite and pulled taut, they devised an electrochemical way to strip layers of graphene off graphite and carefully make non-overlapping layers (this explanation is, obviously, extremely simplified).

2-D Or Not 2-D? That Is The Question

Since then, graphene has been lauded as a wondrous material, touted to be the future saviour of mankind. In fact, so revered is it that in 2010, both Geim and Novoselov received the Nobel Prize in Physics for ‘groundbreaking experiments regarding the two-dimensional material graphene’. That, however, is not exactly correct, as the carbon atoms themselves are 3-dimensional beings. However, the 2-dimensionality refers to the way electrons move on graphene. When we think of graphene as a single sheet  of carbon atoms we can imagine the electron clouds over either side being able to move along the length and breadth of the material but not through the sheet from one side to another. In this regard, the freedom for electron movement in graphene being 2-dimensional makes the material classified as a 2-dimensional one.

Figure 2: 2-Dimensional Electron Movement

It is this precise aspect of graphene that accords it the significant characteristics that make it so superior to others when it comes to certain applications. Firstly, electron movement is much quicker in graphene than it is in any other material. This is, on balance, quite obvious as the electrons in graphene do not undergo resistance from atoms in the third dimension as there are none in the first place. Hence, the electrons behave more like massless points and move close to the speed of light in a vacuum. This, in turn, reduces the amount of energy loss when electrons are transferred through it. Hence, the speed and efficiency of electricity transfer can be greatly increased, leading to ultra-fast charging of batteries, for example.

The reduction of energy losses opens also another avenue for research, into the production of supercapacitors and superconductors. Capacitors are devices that store a charge to be used later (they’re basically simple batteries that can be charged and discharged when necessary). Supercapacitors are just much better performing capacitors that can bridge the gap between the charge that can be stored by capacitors and the much greater ones that can be stored by rechargeable batteries. The interest in developing these exists due to the lack of rigor in rechargeable batteries that can’t handle high numbers of charge-discharge cycles. Graphene can, theoretically, be used to produce these devices.

Moreover, there is also a possibility of graphene being used as a superconductor. Superconductors are materials through which magnetic lines do not flow (they go around them instead). Due to the interconnection of electric and magnetic fields (through electromagnetism), this also causes electrons moving in superconductors to not encounter any resistance. Simply put, electricity which is contained in the material can be indefinitely stored without any source feeding more electricity to it (as there are no losses of energy). For now, superconductors are only encountered at very low temperatures. The highest-temperature superconductor has been found to be hydrogen sulphide at -70 0C but at very high pressures of about 150 gigapascals. Usual high-temperature superconductors operate at lesser than -100 0C. For a while now, much hope has been put on graphene to be used to produce a true high-temperature superconductor that operates at close to room temperature but, for now, graphene superconductivity has been found only in about -230 0C.

Filters, Not Just For Instagram

Finally (for this article but not for graphene), we have the consideration of the extremely small pores of graphene. Any picture of graphene shows hexagonal holes peppering it due to its structure. This is ideal when considering the usage of graphene as a filter. The pore size of graphene, being not much larger than a small factor of the bond length between two adjacent carbon atoms, can be used to filter water to make pure, potable water. The main area for usage of these filters is the desalination of sea water. An extremely large majority of the water on the surface of the earth is made up of undrinkable sea water. Due to that, and a heavy stress placed upon drinkable water resources due to overpopulation, there is a critical need to either produce more water for those who would need it and desalination is one of the best avenues for that. Other than this, there are other, such as purifying sewage water, that can be ameliorated by the usage of graphene as well, as the water molecules are small enough to diffuse through graphene pores but sewage impurities and salt are not.

Figure 3: Graphene As A Filter

It has been shown again how impressive graphene is and yet mysterious still, a full 13 year after being isolated using a bit of Scotch tape and pencil shavings. In fact, with the National Graphene Centre having just been constructed in Manchester (across from the Chemical Engineering building to constantly mock us), there is certainly a lot of hope imparted upon this amazing sheet. However, the great physical strength of graphene that is 200 times as strong as the strongest steel seems to be able to handle it. For now, many have said it is not living up to the hype, but there is always a lag in results in the beginning of research, and the public needs to give graphene the proper amount of time to mature. For the sake of us all.

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