Potential dependence of the step line tension on surfaces in contact with an electrolyte

The potential dependence of the step line tension for electrodes in contact with an electrolyte, but without specific adsorption, is calculated by solving the Poisson–Boltzmann equation numerically. Two contributions to the potential dependence are found. A contribution arising from the step geometry is zero at the potential of zero charge (pzc) and positive for either sign of the potential. The prevailing contribution arises from the dipole moment of the charge distribution at steps. It is approximately proportional to the dipole moment and the specific surface charge, and negative for potentials positive of pzc.