How to convert redox potential vs NHE to energy in absolute scale

To convert energy from absolute scale [given in electron volts] to redox potential with reference to normal hydrogen electrode (NHE) [in Volts] use this equation:

eU_redox_potential_with_reference_to_NHE / e [V]    =    -4.5 [eV]     -     E_Fermi [eV].

Example: Fermi level of Silicon on a vacuum scale is E_Fermi = -4.8 eV, so the corresponding redox potential with reference to NHE is:

U_redox_potential_with_reference_to_NHE   =  -4.5  -  (-4.8)  =  +0.3 V.



Now, the opposite conversion, to convert redox potential with reference to NHE [in Volts] to energy in absolute scale [in Electron Volts], use this equation:

E_Fermi [eV]   =   -4.5 [eV]    -     eU_redox_potential_with_reference_to_NHE / e [V].

Example: Fermi level of Silicon given in redox potential with reference to NHE is +0.3 V, so the Fermi level in absolute scale is:

E_Fermi = -4.5 -0.3 = -4.8 eV.


Use this figure to check your values.

Figure taken from "Zoski, Cynthia G., ed. Handbook of electrochemistry. Access Online via Elsevier, 2007".