Interplay between structure and electrocatalytic activity in flow-engineered three-dimensional porous transport electrodes for alkaline water electrolysis

The bottleneck challenge consisting in the intensification of alkaline water electrolysis can be narrowed down to two components of the overpotential. Activation losses are the most obvious ones, but it often hides the relevance of ohmic losses, especially at industrially relevant current densities. We recently showed that PEM-like performance can be reached in alkaline water electrolysis by using flow-engineered 3D electrodes 1. Under forced upstream electrolyte flow, these laterally-graded structures generate a high velocity field normal to and away from the diaphragm, resulting in a significantly enhanced bubble removal efficiency and the lowest ohmic losses reported in the literature. In the present work, we take the concept further by tuning the structure of these porous transport electrodes (PTEs) and by using highly active coatings. While the electrochemical testing is performed in a home-built setup dedicated to studying the effect of a high forced upstream electrolyte flow, CFD simulations are conducted in parallel, using explicit representations of the porous transport electrodes obtained by micro-computed X-ray tomography.