Dependence of the Reverse Current on the Surface of Electrode Placed on a Bipolar Plate in an Alkaline Water Electrolyzer

The behavior of the leak and reverse currents in a bipolar-type alkaline water electrolyzer has been investigated using a bipolar-type electrolyzer which consists of two cells. The electrodes were nickel mesh, which are the conventional electrodes for alkaline water electrolyzers. The leak circuit could be expressed by a simple equation and a simple equivalent circuit for the cell performance and ionic resistance of the manifolds. The electrolyte was replaced by a gas-free electrolyte after electrolysis to classify the influence of the reverse current into the gas reaction and electrode active material. As a result, the dominant driving force of the reverse current was the active nickel-based materials on the Ni electrode. The redox couples on the electrode surface during the reverse current were estimated based on the measured cell voltages and redox potentials on a nickel electrode. The final potentials of both sides on the bipolar plate for the replacement conditions were higher than those for the non-replacement condition, because the hydrogen of the reductant was removed from the cathode electrolyte, and the balance of the reductant and oxidant would change to the oxidation side.