A standard hydrogen electrode has zero electrode potential because the electrode potential is assumed to be zero.
Standard hydrogen electrode(SHE)
The SHE is the universal reference for reporting relative half-cell potentials. It is a type of gas electrode and was widely used in early studies as a reference electrode and as an indicator electrode to determine pH values. The SHE consists of a platinum electrode immersed in a solution with a hydrogen ion concentration of 1.00M. The platinum electrode is made of a small platinum foil which is platinized (known as platinum black). Hydrogen gas, at a pressure of 1 atmosphere, is bubbled around the platinum electrode.
The Standard electrode potential of SHE is zero volts. This SHE can act as anode or cathode, depending upon the half cell attached to it.
If it acts as a cathode, then the following reaction occurs:
2H+ + 2e– → H2 (Reduction Occurs)
Hydrogen Ion Hydrogen Gas
If it acts as an anode, then the following reaction occurs:
2H – 2e– → 2H+ (Oxidation occurs)