A diffusional model of "water splitting" in electrodialysis

A diffusional model of water dissociation within an unstirred layer in a cross electric field is considered. It is concluded that for realistic values of the bulk salt concentration, the salt ions are potential determining over a wide range of voltages, in particular deeply within the domain of "water splitting". As a corollary, the shift of pH in the unstirred layer is determined by voltage and does not depend on the bulk concentration of the salt, The efficiency of the current depends strongly on the latter. It is shown that the diffusional overvoltage approximation leads to overestimated values of the current carried by the H⁺ and OH^- ions, compared with those obtained by numerical solution of the exact problem.