Process intensification of alkaline water electrolysis by using 3-D electrodes

Hydrogen is a promising and well‐accepted energy vector to store electricity produced by intermittent\nsources, such as solar panels and wind turbines. In order to be cost effective, the water electrolysis needs to be\nintensified (higher production in smaller units) and scaled up to the match the power of electricity sources\nThe current work focuses on a simple way to increase the efficiency of water electrolysis by the use of 3‐D electrodes\nand forced electrolyte flow. Such macro‐porous electrodes allow to reduce the cathodic overpotential compared to\nstate of the art 2‐D plate electrodes. Under natural convection the produced gas bubbles tend to block the 3‐D structure\nreducing its benefit. Thanks to the forced flow, the gas bubbles are forced out of the 3‐D electrodes.\nA typical result is shown in Figure 1. According to the electrokinetic Butler‐Volmer equation, a higher current density\nrequires a higher overpotential. Therefore, since for the same applied current the current density decreases with\nincreasing specific electrode area, the required (over‐)potential to drive the macroscopic current will be lower for the\n3‐D electrode compared to a 2‐D electrode. For this reason the use of 3‐D electrodes will reduce the cell voltage for a\ngiven applied current as it can be seen in Figure 1.\nIn Figure 2, we can see the influence of the catholyte flow rate on the cell voltage. At lower flow rate (v1) the produced\nhydrogen bubbles tend to block the 3‐D structure of the electrode, reducing the surface area in contact with the\nelectrolyte. Increasing the flow rate (v3 to v9) will force de bubbles out of the electrode allowing to take full advantage\nof their high surface area.\nFigures 1 and 2 were obtained in a benchtop laboratory experiment. Future work will focus on implementation of these\nresults in a pilot plant setup. The latter has a size representative for an industrial production equipment. Our\npresentation will show the results of this scale‐up.