Since renewable energy sources supply electricity with temporal fluctuations, efficient energy storage methods play a key role in bridging the gap between generation and consumption. Proton exchange membrane water electrolysis (PEM electrolysis) represents a central technical solution in this context. However, its main disadvantage compared to fossil hydrogen production lies in the high investment costs, which are primarily due to corrosion-resistant components made of titanium with noble metal coatings. In particular, bipolar plates (BPP) and porous transport layers (PTL) account for around two thirds of the system costs. The aim of this work is to reduce the capital costs of PEM electrolysers by developing suitable corrosion protection coatings. For this purpose, PTLs made of stainless steel expanded metals are coated with titanium to investigate whether they can replace conventional PTLs made entirely of titanium. In addition, noble-metal-free coatings are being developed to completely substitute the noble metal layers used so far. Metals, nitrides, alloys and conductive oxides are considered as potential coating materials. Different types of PTLs (felts, expanded metals, sintered bodies) as well as different coating methods are investigated. The focus is on thermal spraying (TS) and magnetron sputtering (MS). In addition, corrosion tests are conducted to evaluate both materials and process parameters. The results of PEM electrolysis experiments carried out at IET-4 show that Ti coatings deposited by cold gas spraying on stainless steel expanded metals can achieve almost identical current densities as conventional titanium-felt-based PTLs and can be operated stably for more than 1000 hours. Furthermore, titanium alloys with niobium or tantalum were produced by magnetron sputtering, which form conductive oxide films under corrosive electrolysis conditions. Initial tests show stable current density over a period of 144 hours. Transmission electron microscopy (TEM) also confirmed the successful incorporation of niobium into the titanium oxide layer. These findings support the hypothesis that targeted doping can significantly increase the conductivity of the forming oxide layers and that noble metal free corrosion protection coatings can be used in PEM electrolysers.
Tim Sievert (Wed,) studied this question.