Cold gas spraying of titanium on stainless steel to enhance corrosion protection inside proton exchange membrane water electrolyzers

In order to meet society's increasing energy needs and at the same time reduce the dependence on fossil fuels, it is essential to expand the production of renewable energies. However, a particular challenge of such energies is the discrepancy between energy production and demand. To bridge this gap, methods are needed to store the energy generated. One possibility is the production of green hydrogen by means of Proton Exchange Membrane Water Electrolysis (PEMWE), which can later be used to generate electricity. Consequently, it is crucial to develop cost-effective and resource-conserving manufacturing methods for electrolyzer stacks. In this study, we compare a conventionally used porous transport layer (PTL) on the anode side, which consists of a titanium felt, with a new type of PTL made out of a stainless steel expanded metal coated with titanium. Cold gas spraying (CGS) was selected as the coating process, which, like the production of expanded metals, is highly scalable. In addition, cold gas spraying has the advantage that the deposition can take place under normal atmospheric conditions, as comparatively low gas temperatures prevent titanium from undergoing any phase changes. This study shows that it is possible to coat 130 μm thin expanded metals without deformation or blockage. The microstructure was analyzed using scanning electron microscopy (SEM) and the phase composition was determined through X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The performance of different PTLs was compared by incorporating them into a proton exchange membrane (PEM) electrolyzer test cell. The newly fabricated PTL reached a current density of 2.6 A/cm² at 2 V, which is only slightly lower than the benchmark value, reached with a full-body titanium felt, of 2.9 A/cm². Compared to the full-body titanium felt, our new titanium-coated stainless steel-based PTL can reduce the amount of titanium needed by 68 %.