Alright, electrochemistry (2) is coming up. Time to write about fuel cells. They are some pretty cool stuff in my opinion. And they are the most important research area in electrochemistry.
The net reaction taking place is pretty basic:
H2 + 1/2 O2 -> H2O
You may probably have heard it before.
Other types oxidise hydrocarbons or alcohols with air oxygen. An important example is the direct methanol fuel cell that this lady at BBC likes to use to power her cell phone.
Using the reaction above for the production of electricity is not quite simple. The trick is that you need an electrolyte that conducts either H+ or O2-.
If you want to conduct H+, the polymer electrolyte membrane fuel cell is your choice. The electrolyte is Nafion an ion exchange membrane based on teflon with sulfonic acid groups. Nafion only lets small cations pass (which is kind of opposite to typical ion exchange). With the help of platinum, hydrogen is stripped of its electrons at the anode. It travels through the Nafion membrane. It reacts with oxygen at the cathode and regains its electrons to form water. The PEM works at 80°-90°C.
You can also have the O2- move around. One way to have that is ZrO2 doped with Y2O3. Next to the yttriums there are oxygen vacancies. At 700°-1000°C its conduction is good enough for use in the solid oxide fuel cell. The solid oxide fuel cell is nothing for your cell phone, rather for a small power plant with good efficiency, especially combined with a Carnot process.
A third type is the molten carbonate fuel cell (300°C). Oxide ions combine with CO2 to from carbonate. Carbonate travels through the fuel cell. CO2 is released at the anode.
Alright that's it for now. I like my internship but coding in Python all day doesn't really make you want to sit in front of your computer after coming home.
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