Science Buddies: "Ask an Expert"

Hi,

I am currently in the process of constructing a microbial fuel cell as according to the information stated in the page on ScienceBuddies, but I have run into a slight problem; I have constructed the cathode chamber already and I know that you are supposed to put the carbon cloth w/the epoxied copper wire inside of the chamber, but I was wondering, what materials should be used for the anode electrode? Can it also be a carbon cloth/copper wire electrode?

If you could reply quickly with a response, it would be much appreciated! THANKS!

Hi VScience,

I have looked at our microbial fuel cell experiment (found here: https://www.sciencebuddies.org/science- ... p026.shtml), and this is how they describe making the electodes.

Making the Electrodes

With the scissors, cut the carbon cloth into four equal squares. Each square should be 5 cm x 5 cm .
Take each of the four pieces of copper wire and with the wire strippers, strip off 6 inches of the insulator on one end of each piece. Strip off 1 centimeter (cm) from the other end of each wire.
Prepare the nickel epoxy according to its directions.
Epoxy the 6 inches of bare copper wire to the carbon cloth along the edges of the square. Repeat with the other three carbon cloths. Let the epoxy harden for 10 hours.

Figure 6. This is a visual of how the electrode should look.

Once the epoxy has hardened, test the connection between the carbon cloth square and the copper wire with the digital multimeter. Turn the digital multimeter to the resistor/resistance mode. Place one lead on the carbon cloth and the other lead on the free bare end of the copper wire. There should be no or very low resistance (1–3 ohms). If there is a large resistance, then remake the electrode.
Repeat steps 1–5 two more times. You need to make enough electrodes to use in three anode-cathode pairs. In other words, you need to make six electrodes. At the end of this section, you will have eight electrodes. Set two of the electrodes aside and keep them as spares.

I however am not very familiar with this project-so hopefully another expert can give you more insights!

Thanks,
Jenny

Dear Science Buddies,
would you help me please, I am making a microbial fuel cell.
I have a problem with making electrodes using instructions from the Science Buddies website: https://www.sciencebuddies.org/science- ... #procedure .

If I follow the instructions, I will have 4x3=12 carbon cloth/wire assemblies for three anode-cathode pairs. I know I need to make six electrodes, 3 cathodes and 3 anodes, but I have 12, so I presume I have to glue two of the assemblies together to make one anode/cathode, am I right? Should I epoxy 2 wire/carbon_cloth assembies together? How should I do it to make it work better?

- a. Should I epoxy 2 pieces of carbon cloth together and wires placed outside?
(I presume that I will need also to epoxy wires together but it does not seem right)
b. Can I epoxy one wire in-between 2 carbon cloth pieces ?

Thank you!

Hi Kristi,

To avoid possible confusion with the previous student's questions, please put your posts into a SEPARATE thread. It is easier for us experts to keep track of which questions and answers go with which student.

I think you are a little confused about the terms anode, cathode and electrode and where they are physically in the fuel cell. An anode IS an electrode and so is a cathode, but in order for the fuel cell to work, they need to be separate. The instructions have you make three fuel cells which means you need three anodes and three cathodes--six electrodes in total--one PAIR for each fuel cell. But calling the electrodes a 'pair' does not mean that they are physically together--just that they are connected through the salt bridge and the external wire.

For each fuel cell there is ONE anode electrode that goes into the left container with the mud and ONE cathode electrode that goes into the right container with the salt solution only. The electrodes are all made the same way with the carbon cloth and the copper wire epoxied to it. Be SURE to use nickel epoxy because it has to conduct electricity and normal epoxy won't.

I hope this answers your question. If you need more help just let us know. Good luck! This is a really cool project and it is amazing that you can get electricity out of a little mud from the bottom of a stream. If you could just keep the bacteria alive you could get free electricity!

Sybee