Pourbaix Diagram
pH-potential diagrams are helpful tools in electrochemistry.
References Electrodes and the Pourbaix Diagram
The so-called Pourbaix diagram gives an overview of the pH dependence of potentials. The potentials are calculated for 25°C in a pH range from pH -2 to pH 16 and plotted against the standard hydrogen electrode (SHE).
A reversible hydrogen electrode (RHE) is a special type of the standard hydrogen electrode (SHE). Unlike the SHE, which requires an electrolyte key, the RHE can be inserted directly into the solution to be measured.
Without an electrolyte key, there is neither ion exchange between the electrode and the sample solution nor diffusion potentials in the RHE.
The potential of the RHE itself changes with the pH of the electrolyte by 59 mV/pH @25°C. This means that for any pH-dependent system changing its potential by 59 mV/pH, you will measure a stable pH-independent potential.
By the way: You can find a helpful online calculator for Pourbaix diagrams here.
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Use of the Hydrogen Electrodes HydroFlex and Mini-HydroFlex
HydroFlex does not contain any interior electrolyte, thus there is no ion-discharge and no diffusion potential.
Here you will find out more about the electrolytes and solutions in which our hydrogen reference electrodes can be used. Also learn more about the use of (Mini-)HydroFlex as a Reversible Hydrogen Electrode, Normal Hydrogen Electrode, and Standard Hydrogen Electrode.
Platinum Plated Platinum Electrode as Standard Reference Electrode
In the past, a platinum plated platinum electrode washed round with hydrogen gas in hydrochloric acid has established itself for this purpose.
If you would like to learn more about this or measuring potentials with the hydrogen reference electrode HydroFlex, you can find further information here.
Basics
Do you need help with basic terms like activity, concentration, potential, and voltage? Learn more here.