What is the standard electrode potential for the hydrogen electrode?

The standard electrode potential for the hydrogen electrode is defined as 0.00 V. This value serves as the reference point against which all other electrode potentials are measured in electrochemistry. The hydrogen electrode is considered the standard because it involves the half-reaction:

[ \text{2H}^+ + 2e^- \leftrightarrow \text{H}_2(g) ]

At standard conditions (1 M concentration of H⁺, 1 bar pressure for H₂, and 25°C), this reaction is set to have a potential of zero. This convention provides a consistent basis for comparing the potentials of other half-reactions. All other electrode potentials are reported relative to this standard, making it fundamental to electrochemical studies.

This means that other values listed, such as +0.83 V, -0.40 V, and -1.23 V, represent potentials of other half-reactions compared to the hydrogen standard and do not reflect the inherent potential of the hydrogen electrode itself. Hence, the value of 0.00 V is the accepted standard for the hydrogen electrode in electrochemistry.