Overpotential-induced lability of the electronic overlap factor in long-range electrochemical electron transfer: charge and distance dependence

Long-distance electrochemical electron transfer exhibits approximately exponential dependence on the electron transfer distance. On the basis of a jellium model of the metal surface we show that the slope of the logarithm of the current vs. the transfer distance also depends strongly on the electrode charge. The slope is smaller the more negative the charge density due to enhanced extension of the surface electronic density profile on the solution side, and thereby better electronic overlap with the reacting molecule. The effect is sensitive to the bulk electron density of the metal and the localization of the electronic state at the molecular reactant site. Effects similar to these have been observed experimentally and could be common for electronically light metals.