Understanding the Standard Hydrogen Electrode (SHE)
The Standard Hydrogen Electrode serves as the universal baseline thermodynamic benchmark for reporting electrochemical half-cell potentials. By definition, its standard potential is set to zero volts at all temperatures under standard state conditions. However, real-world laboratory conditions vary in temperature, solution acidity, and gas pressure, which shifts the actual operating voltage away from zero. Using our advanced calculator helps researchers accurately adjust for these non-standard parameters effortlessly.
Formula Used in This Calculator
The calculation is derived from the Nernst equation applied to the hydrogen half-cell reaction: $2H^+ + 2e^- \rightleftharpoons H_2$. The mathematical formula computes the potential ($E$) as follows:
$$E = E^\circ - \frac{RT}{nF} \ln\left(\frac{P_{H_2}}{a_{H^+}^n}\right)$$
Where $R$ is the universal gas constant, $T$ is the absolute temperature in Kelvin, $F$ is the Faraday constant, $n$ represents the moles of electrons transferred, $P_{H_2}$ is the partial pressure of hydrogen gas, and $a_{H^+}$ denotes the activity of hydrogen ions calculated via solution pH.
How to Use This Calculator
- Input your target operating temperature in degrees Celsius into the thermodynamics panel.
- Specify the hydrogen gas pressure in atmospheres.
- Enter the exact pH level and ionic activity coefficient of your test solution.
- Configure advanced parameters like electron stoichiometry and standard potential if required.
- Click the calculate button to instantly review your precise electrode voltage results above the form.