I am looking to construct my first photocatalytic fuel cell. I want to construct a membrane electrode assembly for it to reduce the inter electrode distance and thus decrease the proton diffusion distance. However, most schematics and explanations I have seen do not explain how electrons freed during oxidation at the anode travel to the current collection plate (i.e., the component that transfers current from the anode to the cathode) and then to the cathode if these components are not in contact. Or are they touching and the schematics do not show that? I would be most grateful for any explanations, references, or recommendations. Thank you.
Hello Andrew,
I am not sure if I am understanding your question, but let me try, to answer, you are saying " (i.e., the component that transfers current from the anode to the cathode)", in fuel cells electrons do not cross directly from anode to cathode "within the cell", they should not. Electrons have to travel through the external circuit, so you have the produced electricity (current) output form the cell.
I hope this helps
I think my question was not well worded. In hydrogen fuel cells that use a membrane electrode assembly (MEA), the anode and cathode are only separated by a proton exchange membrane such as Nafion. The schematics I have seen do not connect the external circuit connections (e.g., alligator clips or epoxied copper wires) to the anode and cathode directly, maybe because they are so thin. Instead there is often two metal plates (one on each side of the cell) labeled as "current collector" plates that transfers electrons from the anode side to the cathode side. However, the current collectors are not in contact with the electrodes and I am wondering how the electrons get from the anode to the current collector (i.e., the external circuit). Please see the picture attached I found on the internet. Thank you for your reply.
dear Andrew
I am not sure about your question,, but I think it is not so much complicated. Basic principle of hydrogen fuel cell is, hydrogen is oxidized by the oxidizing agent at anode the hydrogen ion move toward cathode through membrane, where it is combined with oxygen to form water. The electron released in oxidation of hydrogen at anode is the output current which is collected in external circuit.
Hi Andrew,
If I understand your question correctly the answer you're looking for is that the gas diffusion layer (normally made from carbon fibers) and the graphite plate are both electron conductive which allows the electrons to move from the electrodes to the current collectors.
From that point on you can attach the alligator clips or whatever you choose to the current collectors and gather the current produced by the fuel cell.
I hope that answers your question.
Regards, Andrej
In the case of the electrode and the current collectors, often the electrode is actually 'cast' or spread onto the current collector. Whatever form the electrode takes, it is simply touching the current collector and that is (usually) enough for an electrical contact.
The two current collectors are then certainly connected to each other, usually across a 'load'. This depends upon why you are doing the experiment; if it's for a demo it's connected to a light bulb or a digital clock, if it's for measurement it's connected to a measurement device, or if you simply care about the redox products then it can be short-circuited (i.e. a wire connects the two current collectors).
If the two current collectors are not connected, there will be no oxidation/reduction of the fuel at either electrodes because, as you pointed out, there is no way for the electrons to flow from one electrode to the other without that external connection.
This is a zoomed out image! http://www.deskeng.com/de/img/modeling-fuel-cells_1.jpg
Further to what Rami said, the gas diffusion layer and membrane need to be an ion conductor (e.g. proton conducting) but most certainly do not conduct electrons. Many people call it 'electrically conductive'; this is technically correct, but results in some people mistaking 'electrically conductive' as 'conductive to electrons'. For electrolytes these two concepts are not the same.
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