Question

What is the difference between the Normal Hydrogen Electrode (NHE) and the Reversible Hydrogen Electrode (RHE)?

- Also, if a redox happens at the NHE of 0.2 V, please calculate the potential for the RHE at pH = 1.

Answer 1

he standard hydrogen electrode and/or the normal hydrogen electrode are the most important reference electrodes, since their potential is defined as the zero point of the electrochemical series.

They consist of a platinized platinum plate that is immersed into an acid solution. The platinum plate is bathed with hydrogen gas. The hydrogen adsorbs on the platinum to form equilibrium with the hydronium ions in the acidic solution. Platinum is used as a catalyst for this potential-determining reaction:

The potential of the standard hydrogen electrode is defined for a hydronium ion activity of 1 mol/l and saturated with hydrogen gas with a fugacity referred to the standard pressure of 100 kPa (1,000 bar) at all temperatures to 0,0 volts.

In the reversible hydrogen electrode, there is no libration of Cl^– or SO₄^2- by the electrolyte and no diffusion potential. We can use the reversible hydrogen electrode for long time. It is very easy to use. The voltage across the electrodes increases as the current density at the electrodes increases. So that we can measure the equilibrium potential without loss of power.