Effect of molecular chlorine diffusion on theoretical potential-current density relations for chlorine evolving electrode

The effect of molecular chlorine diffusion upon the theoretical potential-current density relations was calculated for chlorine evolution according to the Volmer—Tafel mechanism as well as the Volmer—Heyrowsky mechanism. It has been found that a minimum Tafel slope of 29.6 mV at 298 K occurs for both mechanisms. This slope occurs for the Volmer—Tafel mechanism when either the Tafel reaction or the chlorine diffusion, away from the electrode surface into the bulk of solution, is the rate-determining step, and for the Volmer—Heyrowsky mechanism when it is the chlorine diffusion that is the rate-determining step. Moreover, it has been established that only a careful use of both the polarization resistance at the reversible potential and the stoichiometric number from this deduced, is allowed to elucidate the mechanism of electrode reactions with adsorbed atomic intermediates.