What Is the Hydrogen Fuel Cell Nernst Reversible Voltage Calculator?
The Nernst equation calculates the maximum theoretical electrical potential that can be extracted from the electrochemical reaction H2 + 0.5 O2 -> H2O.
How Does the Hydrogen Fuel Cell Nernst Reversible Voltage Calculator Work?
Combines temperature-dependent Gibbs free energy change delta_G with reactant gas activities to determine the thermodynamic potential.
Hydrogen Fuel Cell Nernst Reversible Voltage Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
E_{ ext{Nernst}} = E^0(T) + rac{R T}{2 F} lnleft( P_{H_2} sqrt{P_{O_2}}
ight), quad E^0(T) = 1.229 - 0.00085 (T - 298.15)
Nernst thermodynamic potential equation for hydrogen-oxygen electrochemical fuel cells.
How to Use the Hydrogen Fuel Cell Nernst Reversible Voltage Calculator
- Input operating temperature in Kelvin, reactant gas partial pressures in atmospheres, and operational load current density.
Step-by-Step Example Calculation
Automotive PEM Fuel Cell at 80°C
Input Values:
tempKelvin:353.15
h2PartialPressureAtm:2.5
o2PartialPressureAtm:1.8
currentDensityACm2:0.65
Worked Steps: Standard potential E0 = 1.182 V, Nernst OCV = 1.216 V, Net operating voltage = 0.731 V at 0.65 A/cm².
Understanding Your Result
Displays open-circuit Nernst voltage, standard potential E0(T), activation overpotential, and net cell terminal voltage under load.
Factors That Affect the Result
- Higher operating temperature lowers reversible voltage (negative entropy change), but increases reaction kinetics and membrane conductivity.
When Should You Use This Calculator?
- Sizing fuel cell stacks for zero-emission vehicles, stationary microgrids, and electrolysis round-trip efficiency studies.
Assumptions & Limitations
- Assumes liquid water product at PEM temperatures and typical 0.15 ohm-cm² area-specific resistance.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard electrochemical thermodynamics formulation.