A Novel Two-Step Water-Splitting Electrochemical Cycle for Hydrogen Production

Abstract

We propose a novel electrochemical water-splitting cycle consisting of two-step electrochemical reactions for oxygen and hydrogen production by introducing an intermediate electrode. Two-step water electrolysis offers the following advantages: (i) higher-purity hydrogen can be obtained because hydrogen and oxygen gases are generated in different steps and (ii) high energy conversion efficiency for hydrogen production can be achieved by reducing the ohmic overpotential between the electrodes through the use of a thinner separator than a conventional one. Furthermore, a pulsed current can be supplied to the electrolysis cell, which leads to a low concentration overpotential by increasing the reacting species concentration in a diffusion layer. In the present study, manganese dioxide (MnO 2 ) was selected as the intermediate electrode because its oxidation-reduction potential is located between the potentials of the hydrogen and oxygen evolution reactions.