Using the method of matched asymptotic expansions, an approach has been suggested for obtaining the current/potential curves of a spherical electrode in electrolyte solution, taking into account the kinetics of electrode processes. Asymptotically exact expressions for current/potential curves have been obtained for complex kinetics in the general case of a redox reaction, and in more detail for a simple neutralization reaction both for the case of a "pure" electrolyte and for a dilute electrolyte. A correction term has been derived for the equation of the potential of Helmholtz sphere, which considers the influence of current and the diffusion limitations, upon this potential. The zero charge potential point for a spherical electrode is shown to be different from the electrolyte zero potential.