Photoelectron injection into dilute electrolyte solutions: Part 1. Methodology

Abstract

A general algorithm for the numerical solution that describes the diffusion and reactions of particles in an arbitrary potential was used to calculate the photodiffusion currents in dilute electrolyte solutions in terms of the exact Gouy-Chapman expression for the diffusion potential φ( x). The solution has been obtained for the simplest case when the product of the capture of solvated electrons, generated by photoinjection, is a neutral radical. The limited applicability of the exponential approximation of the φ( x) potential has been demonstrated. When the electrolyte solution is dilute, the characteristic time of the return of solvated electrons e s − to the electrode increases by 3–6 orders of magnitude within the negative potential range. Thus, when the scavenger concentration is 10 −4-10 −3 M, it can fully capture e s −. The calculation results have been compared with those of experiments performed in diluted aqueous solutions of NaF (10 −3-1 M) at wavelengths of λ = 428-193 nm. The mean distances determined between e s − and the photoelectrode are in fair agreement with the previous data obtained for concentrated aqueous electrolyte solutions. We have also found the mean distances, photoinjection threshold and full photoinjected charge in methanol. The effect of the intensity of light on the value of photo-induced charge has also been demonstrated.