Effect of d-Metal Hydroxides on Water Dissociation in Bipolar Membranes

Methods of electrochemical impedance, voltammetry, and ion transport numbers are used to study bipolar membranes that contain hydroxides of transition metals on the bipolar boundary. It is shown that the introduction of hydroxides significantly increases the rate of water dissociation in bipolar membranes, and the catalytic activity of transition metal compounds depends on the nature of the metal. It was found that the pseudounimolecular rate constants of the rate-limiting steps of dissociation calculated from the thermodynamic and kinetic data are two orders of magnitude higher than the effective constants derived from experiment. This suggests that only a small fraction of the surface of metal hydroxide particles is in the space-charge region (bipolar region), in which the dissociation of water molecules occurs in high-intensity electric fields.