Fuel cell open circuit voltage and pressure of reactants

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SUMMARY

The discussion centers on the application of the Nernst equation to calculate the open circuit voltage (OCV) of a fuel cell using dry gases. The equation is presented as E(OCV) = E0 + ln(PH2 * PO2^0.5) when water is not present in the circuit. The participants clarify that at open circuit conditions, water should be neglected, as it is not produced without a closed circuit. This highlights the importance of understanding the conditions under which the Nernst equation is applied, particularly in the context of gas mixtures.

PREREQUISITES
  • Nernst equation fundamentals
  • Understanding of open circuit voltage (OCV)
  • Knowledge of gas laws and partial pressures
  • Basic principles of electrochemistry
NEXT STEPS
  • Study the Nernst equation in detail, focusing on its applications in electrochemical cells
  • Research the effects of humidity on fuel cell performance
  • Explore the relationship between gas composition and electrochemical reactions
  • Learn about the impact of temperature and pressure on OCV in fuel cells
USEFUL FOR

Electrochemists, fuel cell researchers, and students studying electrochemical systems will benefit from this discussion, particularly those interested in the effects of reactant conditions on voltage output.

Mr bboy
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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 !
 
Chemistry news on Phys.org
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?
 

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