Nb-Ti alloy coatings for anode PTLs in PEM water electrolyzers

One of the most cost-intensive components of proton exchange membrane water electrolyzers (PEMWE) are the anode-side Porous Transport Layers (PTLs), often comprised of titanium with a noble metal coating such as platinum. Replacing the noble metal coating is crucial to reduce the manufacturing costs of PEM electrolyzers. This study aims on to replace conventional platinum coatings with titanium-niobium alloy coatings using magnetron sputtering. To evaluate the performance and stability of the coated PTLs, laboratory-scale tests have been conducted with PEMWE single cells. Post-mortem analysis of the PTLs included scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and resistance measurements. So far, the best results were achieved with alloy coatings consisting of 94 at.% titanium and 6 at.% niobium, as these coatings enabled stable PEMWE operation for 144h at 2.0V. TEM confirms that niobium is incorporated into the growing oxide scale. We assume that the pentavalent niobium atoms serve as donator sites in the oxide increasing its electric conductivity.