So I have successfully created a graphene capacitor using pieces of graphene burned using the light scribe drive. Not the original pattern that I had hoped to use with the circuit board patterns but a capacitor nonetheless. I decided to use the half disk of full burned graphene I had to build some capacitors while I was waiting for the circuit patterns to finish burning. So yesterday morning I started with a glass microscope slide and two pieces of graphene to create a parallel plate capacitor and to use the glass as the dielectric and seal the whole capacitor with kaptom tape. The diagram would look something like this:
Parallel Plate Capacitor Diagram
I finished making this first test capacitor on glass and it looked like this:
Graphene-Glass-Graphene Parallel Plate Capacitor
So naturally I was excited to test it out after all this waiting I finally had something that looked somewhat complete although it was not the original idea. I hooked it up to a 9V battery and let it charge for about 5 seconds, after that I put a multimeter on it to check voltages, and it only read .26V! It barely held a 1/4 volt! I was at first really confused. So I did a little reading up on a website about graphene and super capacitors, the same website I ordered my graphene solution from and read some very interesting information.
“A conventional capacitor is made up of two layers of conductive materials (eventually becoming positively and negatively charged) separated by an insulator. What dictates the amount of charge a capacitor can hold is the surface area of the conductors, the distance between the two conductors and also the dielectric constant of the insulator. Super capacitors are slightly different in the fact that they do not contain a solid insulator.
Instead the two conductive plates in a cell are coated with a porous material, most commonly activated carbon, and the cells are immersed in an electrolyte solution. The porous material ideally will have an extremely high surface area (1 gram of activated carbon can have an estimated surface area equal to that of a tennis court), and because the capacitance of a supercapacitor is dictated by the distance between the two layers and the surface area of the porous material, very high levels of charge can be achieved.
While super capacitors are able to store much more energy than standard capacitors, they are limited in their ability to withstand high voltage. Electrolytic capacitors are able to run at hundreds of volts, but super capacitors are generally limited to around 5 volts. However, it is possible to engineer a chain of super capacitors to run at high voltages as long as the series is properly designed and controlled. “
I knew I had to use the potassium chloride solution in the capacitor and thought it a bit weird I wasn’t using it in the capacitor I built. Well thats because you have to use a gel or liquid electrolyte in a graphene capacitor to fill the voids in the graphene and thats what makes the capacitor work, its like having millions of tiny capacitors on one tiny sheet of single layered graphene all working together to produce the larger capacitor. Its no wonder my first build didn’t work and only could hold a voltage of .26 volts and had a capacitance of 25 pico-farads (pF) which is almost nothing.
I then tried a capacitor build on the table using a model diagram from a youtube video found at : https://www.youtube.com/watch?v=K7E5NSFJIYU that I watched in which a capacitor was build with a piece of buffed graphene on glass with a paper towel soaked in salt water and aluminum foil as a electrode. Is it crude and poorly put together, probably. But it does work. My capacitor was slightly different in that I used copper tape as my electrode and Potassium Chloride solution as my electrolyte instead of salt water. My capacitor looked like this :
Graphene with copper tapped electrodes and Potassium Chloride soaked paper towel.
This capacitor was able to charge up to 1.1V and hold a charge of over 1V for about one minute before it dropped off to .7V for another two minutes and then held a charge of .45V for another three before it dwindled out. Also this capacitor had a average capacitance of about 25-26 nano-farads(nF). When compared to the first capacitor on glass without the electrolyte solution this capacitor had an average capacitance 1000x higher than the parallel plates glass capacitor. Oh, just another thing a scale below shows capacitance values.
1 Farad is the same as
1 000 000 micro Farads is the same as
1 000 000 000 nano Farads
1 000 000 000 000 pico Farads
So now having at least a somewhat working capacitor I decided I would try it out sealed on a piece of glass with a small piece of denser soaked paper and two copper electrodes on a piece of graphene on a microscope slide sealed with kaptom tape. My capacitor looked like this:
Graphene Capacitor on glass with two copper(tape) electrodes with a potassium chloride soaked paper electrolyte.
Excited to test this capacitor out I charged it up with the 9V and put a multimeter on it and it read 1.7V!! It quickly dropped to 1.5V then 1.4V where it hovered for two to three minutes before dropping to a 1V for another three minutes and finally down to .5 for over twenty minutes! Also this capacitor had a high capacitance over just over 73nF almost triple the previous capacitor that was just on the table. Below is a picture of the capacitor connected to a capacitance meter with a meter output of 73.1nF.
Capacitance Meter with a reading of 73.1nF
I also checked the capacitor for any discrepancies with the potassium chloride electrolyte, kaptom tape, or copper tape just to make sure no voltage was being stored in them or giving me an incorrect capacitance reading. I did this by just using a glass slide with a soaked potassium chloride paper square and two copper electrodes sealed with kaptom tape. Below is a picture:
Soaked Electrolyte paper with copper electrodes-sealed with kaptom tape on a glass slide.
The capacitance meter barely read .02 pF and when charged with a 9V and measured with the multimeter it only read a charge of .18V for less than thirty seconds before it dissipated. This meant that my readings were close to accurate and that the energy was actually before stored in the graphene!
I finally had a working capacitor!! Not the original circuit pattern that I had hoped for but still working and designed well enough to show someone what a graphene capacitor is, I am hoping to try and get a interdigitated circuit pattern capacitor built this week as well, but my my next thought was how could I get this capacitor to show it had power storage and demonstrate it to someone. So we have these little LEDs in the Innovation-Lab that needs about 3Volts to power up. I built two more capacitors exactly like the last. All had a capacitance between 68nF-73nF and could hold about 1.4V-1.7V. Then I looked up series and parallel wiring diagrams to make sure I knew what I was doing when wiring them together. Below are three diagrams that illustrate the difference with visuals and equations:
Basically what these diagrams illustrate is that when capacitors are wired in parallel voltage acceptance does not increase as in (V1=V2=Voltage) but capacitance increases as in (C1+C2=Capacitance), and vice versa for series wiring meaning that voltage acceptance increases(V1+V2=Voltage) but capacitance is lowered as in (1/C1+1/C2=Capacitance).
So obviously I needed to increase the voltage to achieve the needed minimum of 3V so series wiring was the way to go. My series looked like this :
Three Capacitors wired in series.
The capacitance was low but the voltage after the initial charge was about 3.4V and of which this capacitors wired series held for over three minutes. Enough to run a small LED, I think so!! Below is a picture of three capacitors wired in series connected to a small board with a LED in it:
Three Capacitors wired in series powering an LED.
The LED stayed powered up for about two minutes before the voltage dropped below 2.9V which was not enough to power the LED. But I was able to power it up for some time! This is a breakthrough for me because I actually now have something that works! The next step that I will be taking will be to increase the surface area of the capacitors by building new capacitors which will increase capacitance as well as voltage, these new capacitors will have larger pieces of graphene than the previous as soon as I have another full disk burned. I also want to look into getting LEDs that have a lower voltage input so I can power them off of one or maybe two capacitors. Also I will be trying to build a capacitor with the interdigitated circuit patterns that will hopefully be finished burning today! But for now I am excited with what I have accomplished the past three days!