where the standard chemical potential of electrons ( µ e ) is an intrinsic material property and independent of the electrode potential. ∆ M S ϕ = ϕ Mϕ S stands for the inner potential difference, i.e. the electrostatic potential difference between the bulk of electrode (M ) and solution (S) as depicted in Figure . K is a constant defining the reference scale, which in DFT simulations has been realized in two ways. The most conventional choice in DFT calculations is to reference the single electrode potential against the electrostatic potential in vacuum or the bulk part of an explicit or implicit solvent. With this choice, the single electrode potential is ]