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| Hauptseite > Publikationsdatenbank > Reducing the noble metal and titanium content of anode PTLs in PEM water electrolysis - performance and degradation |
| Hauptseite > Publikationsdatenbank > Reducing the noble metal and titanium content of anode PTLs in PEM water electrolysis - performance and degradation |
| Book/Dissertation / PhD Thesis | FZJ-2026-03711 |
2026
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-973-2
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-03711
Abstract: Among the industrialized processes of water electrolysis, proton exchange membrane water electrolysis (PEMWE) has been demonstrated to exhibit high efficiency, thus contributing to the production of green hydrogen and playing a crucial role in decarbonizing the production of fundamental chemicals such as ammonia and methanol. Additionally, PEMWE can contribute to the electrification of our energy system, a pivotal step in the transition to a low-carbon economy. Nonetheless, the financial outlay required for this undertaking is substantial, primarily due to the employment of noble metal catalysts and noble metal-coated titanium porous transport layers (PTLs). Therefore, this work investigated two approaches to reduce the use of precious metals on PTLs and the reduction of titanium as a base material. The first approach involved noble metal free coating materials for the anode PTL, which have not yet been researched as PTL coatings or have been investigated with inconsistent results. The materials involved titanium nitride, tungsten, indium tin oxide, niobium, tantalum and titanium-niobium and titanium-tantalum alloys. Their deposition was carried out by the institute IMD-2 using physical vapor deposition (magnetron sputtering) and thermal spray techniques (atmospheric and vacuum plasma spraying as well as cold gas spraying). While magnetron sputtering provided dense and thin coatings of just a few micrometers, thermal spray processes yielded thicker coatings between 30 μm and 60 μm. The coated PTLs were investigated for their stability in PEMWE single cell operation using electrochemical impedance spectroscopy (EIS), ex-situ resistance measurements and scanning electron microscopy (SEM) with elemental analysis via energy dispersive X-ray spectroscopy (EDX). The experiments revealed, that almost all materials underwent oxidation, resulting in increased ohmic resistances and decreased cell performances. Only coatings consisting of a mixture of 6 at.% niobium or tantalum and 94 at.% titanium provided a significant enhanced stability over 144 h. However, also pure magnetron-sputtered Ti layers enabled stable PEMWE performance close to the alloy coating. Hence, the influence of niobium and tantalum in the titanium layer on the preservation of the conductivity of the forming oxide scale has not yet been conclusively proven. Due to the insufficient oxidation stability of the materials that were selected based on their reported corrosion stability under simulated PEMWE conditions in the literature, additional investigations addressed the question to what extent ex-situ corrosion tests can reflect the oxidation and corrosion stability of anode PTL coatings. For rapidly oxidizing TiN coatings, it was found that the conditions set in the corrosion cell (pH 1.16 and potentials of 1.4 V and 1.6 V vs. RHE) led to stronger oxidation than for coatings in PEMWE experiments at 1.5 V and 2.0 V cell voltage. Consequently, it was found, that ex situ tests under the conditions most commonly used in the literature to date (sulfuric acid and potentials up to 2.0 V) are not adequate for simulating the oxidation of PTL coatings. The second approach aiming for reduction of the amount of Ti used consisted of titanium-reduced and stainless steel-based anode PTLs as an alternative to full titanium PTLs. As stainless steel requires a corrosion protection layer, magnetron sputtered (PVD) layers with a thickness <10 μm were deposited on stainless steel meshes and felts and cold gas sprayed (CGS) Ti layers with a thickness between 33 ± 14 μm and 60 ± 12 μm on meshes. The results with thin coatings on the two different substrates differed greatly. While the mesh showed extensive pitting corrosion, the felt PTL was only subject to surface corrosion with increasing cell performance even after more than 1000 h of operation, whereby membrane thinning could not be ruled out, explaining a substantial part of the performance improvement. As the two substrates were provided by different suppliers, they exhibited slightly different proportions of alloying elements. Consequently, the results indicate a correlation between stainless steel composition and corrosion resistance, requiring further systematic research. Sufficient corrosion protection of the 316L mesh-based PTLs was only achieved with a 60 ± 16 μm thick CGS titanium coating (CG-60). During the experiments, the effluent water from the anode and cathode sides was screened for emission of stainless steel components via inductively coupled plasma mass spectrometry (ICP-MS). With thinner CGS Ti layers (48 ± 16 μm and 33 ± 16 μm), increased emission of stainless steel components was observed, underscoring superior corrosion protection provided by the thicker coating. All Ti-coated stainless steel substrates had to be sputtered with an additional 38 nm Pt contact layer to prevent titanium oxidation, enabling the CG-60 PTLs to achieve comparable performance and stability over 1000 h at 2.0 V cell voltage to commercial Pt-coated Ti felt PTLs while saving approximately 25 % titanium. Finally, performance data were extracted from dynamic wind profile operation of PEMWE single cells with state-of-the-art PTLs, providing a starting point for the analysis of PEMWE cells with new components. The methods developed for this purpose allow characterization during dynamic operation without having to interrupt the operation to record I-V curves or impedance spectra. Theextracted performance indicators include cell voltage changes, I-V curves and ohmic resistances as well as indications of changes in catalyst activity.
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