A catalyst material containing platinum nanowires supported on single-walled carbon nanotubes (CNTs) is tested thoroughly for the use as a cathode catalyst for polymer electrolyte membrane water electrolyser (PEMEL). The Nafion ionomer content, the platinum to CNT ratio and the thickness of the catalyst layer (CL) is optimized. Long-term measurement with constant current and start-stop cycling of the optimized CL is performed in order to study the durability of the catalyst material. The CLs are characterized ex-situ with TEM, XRD and Raman spectroscopy. During the constant current operation, platinum experiences Ostwald ripening type of degradation and during the cycling, particle agglomeration. The magnitude of platinum degradation is, however, lower than for a commercial Pt/C type of catalyst. Moreover, the CNTs are subjected to carbon corrosion, but the rate of corrosion is observed to be decreasing. Therefore, carbon nanotubes are considered more suitable support material for the cathode catalyst of PEMELs. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.