Comprehensive investigation of novel pore-graded\ud gas diffusion layers for high-performance and costeffective\ud proton exchange membrane electrolyzers

摘要

Hydrogen produced by water electrolysis is a promising storage medium for renewable energy. Reducing\udthe capital cost of proton exchange membrane (PEM) electrolyzers without losing efficiency is one of its\udmost pressing challenges. Gas diffusion layers (GDL), such as felts, foams, meshes and sintered plates, are\udkey stack components, but these are either inefficient or expensive. This study presents a new type of GDL\udproduced via vacuum plasma spraying (VPS), which offers a large potential for cost reduction. With this\udtechnology, it is possible to introduce a gradient in the pore-size distribution along the thickness of the\udGDL by varying the plasma parameters and titanium powder particle sizes. This feature was confirmed by\udcross-section scanning electron microscopy (SEM). X-ray computed tomography (CT) and mercury\udintrusion porosimetry allowed determining the porosity, pore radii distribution, and pore entry distribution.\udPore radii of ca. 10 mm could be achieved in the layers of the GDL close to the bipolar plate, while those in\udcontact with the electrodes were in the range of 5 mm. The thermally sprayed Ti-GDLs allowed achieving\udPEM electrolyzer performances comparable to those of the state-of-the-art sintered plates and far superior\udthan those of meshes. Moreover, a numerical model showed that the reduced capillary pressure and\udtortuosity eliminates mass transport limitations at 2 A cm-2. The results presented herein demonstrate a\udpromising solution to reduce the cost of one of the most expensive components of the stack.