Proton exchange membrane-like alkaline water electrolysis using flow-engineered three-dimensional electrodes
Fernando Rocha, Christos Georgiadis, Kevin Van Droogenbroek, Renaud Delmelle, Xavier Pinon, Grzegorz Pyka, Greet Kerckhofs, Franz Egert, Fatemeh Razmjooei, Syed-asif Ansar, Shigenori Mitsushima, Joris Proost
Abstract
For high rate water electrolysers, minimising Ohmic losses through efficient gas bubble evacuation away from the active electrode is as important as minimising activation losses by improving the electrode’s electrocatalytic properties. In this work, by a combined experimental and computational fluid dynamics (CFD) approach, we identify the topological parameters of flow-engineered 3-D electrodes that direct their performance towards enhanced bubble evacuation. In particular, we show that integrating Ni-based foam electrodes into a laterally-graded bi-layer zero-gap cell configuration allows for alkaline water electrolysis to become Proton Exchange Membrane (PEM)-like, even when keeping a state-of-the-art Zirfon diaphragm. Detailed CFD simulations, explicitly taking into account the entire 3-D electrode and cell topology, show that under a forced uniform upstream electrolyte flow, such a graded structure induces a high lateral velocity component in the direction normal to and away from the diaphragm. This work is therefore an invitation to start considering PEM-like cell designs for alkaline water electrolysis as well, in particular the use of square or rectangular electrodes in flow-through type electrochemical cells. Efficient gas bubble removal is crucial for high-rate water electrolysis aimed at optimizing hydrogen production. Here, the authors show that integrating 3-D foam electrodes into a specially designed cell configuration enables alkaline water electrolysis to perform comparably to advanced systems, thereby enhancing overall efficiency.