Fuel cell open circuit voltage and pressure of reactants

In summary, the conversation is about the Nernst equation at open circuit voltage. The equation is E(OCV) = E0+ ln (PH2*PO2^0.5 / PH2O), but the question arises about what happens if there is no water present in the circuit. The answer is that the equation becomes E(OCV) = E0+ ln (PH2*PO2^0.5 ) and water is neglected. The conversation also touches on why water is taken into account in the equation, even though it is not created in an open circuit. It is suggested that the equation may be applied to a dry gas mixture instead of a solution.
  • #1
Mr bboy
8
0
Hello,

I have some questions regarding the nernst equation at open circuit voltage.

We know E(OCV) = E0+ ln (PH2*PO2^0.5 / PH2O)

I have some trouble with this:
If I have dry gas (both for O2 and H2), and my circuit is open at 25°C and 1 atm I have no water in the circuit so what become the nerst equation ? We have to neglect H2O?
E(OCV) = E0+ ln (PH2*PO2^0.5 )

I am wondering why at OCV we take into account water since we don't create water because the circuit is open, and the only way that we could have water is from the reactants?

Thank you for yout help !
 
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  • #2
First time I hear about applying Nernst equation to a dry gas mixture. Are you sure you don't misread something and you don't deal with a solution, saturated with hydrogen and oxygen, each at 1 atm?
 

1. What is the relationship between fuel cell open circuit voltage and pressure of reactants?

The open circuit voltage of a fuel cell is directly affected by the pressure of the reactants. As the pressure of the reactants increases, the open circuit voltage also increases. This is because higher pressure results in a higher concentration of reactants, which leads to a more efficient chemical reaction and a higher voltage output.

2. How does the open circuit voltage of a fuel cell change over time?

The open circuit voltage of a fuel cell can decrease over time due to a variety of factors. These include the degradation of the catalyst, build-up of impurities, and changes in the membrane's properties. It is important to regularly monitor and maintain a fuel cell to ensure optimal performance and prevent a decrease in open circuit voltage.

3. Can the pressure of the reactants be adjusted to increase the open circuit voltage of a fuel cell?

Yes, the pressure of the reactants can be adjusted to increase the open circuit voltage of a fuel cell. However, it is important to note that there is an optimal pressure range for each type of fuel cell, and exceeding this range can have negative effects on the performance and lifespan of the fuel cell.

4. How does the temperature of the fuel cell affect its open circuit voltage?

The temperature of a fuel cell can significantly impact its open circuit voltage. In general, as the temperature increases, the open circuit voltage also increases. This is because higher temperatures facilitate faster reactions and improve the efficiency of the fuel cell.

5. Is there a specific type of reactant pressure that is ideal for all fuel cells?

No, the ideal reactant pressure varies depending on the type of fuel cell and its specific design. It is important to follow the manufacturer's recommendations for the optimal pressure range for a particular fuel cell to ensure its optimal performance and longevity.

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