# A standard hydrogen electrode has zero electrode potential because

$\begin{array}{1 1}\text{hydrogen is easiest to oxidise}\\\text{this electrode potential is assumed to be zero}\\\text{hydrogen atom has only one electron}\\\text{hydrogen is the lightest element}\end{array}$

Answer : this electrode potential is assumed to be zero
The standard potential of hydrogen electrode is assumed to be zero at all temperature.
The Standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be 4.44 ± 0.02 V at 25 °C, but to form a basis for comparison with all other electrode reactions, hydrogen's standard electrode potential $(E^0)$ is declared to be zero volts at all temperatures.
edited Feb 19