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The present paper presents one- and two-step approaches for electrochemical Pt and Ir deposition on a porous Ti-substrate to obtain a bifunctional oxygen electrode. Surface pre-treatment of the fiber-based Ti-substrate with oxalic acid provides an alternative to plasma treatment for partially stripping TiO2 from the electrode surface and roughening the topography. Electrochemical catalyst deposition performed directly onto the pretreated Ti-substrates bypasses unnecessary preparation and processing of catalyst support structures. A single Pt constant potential deposition (CPD), directly followed by pulsed electrodeposition (PED), created nanosized noble agglomerates. Subsequently, Ir was deposited via PED onto the Pt sub-structure to obtain a successively deposited PtIr catalyst layer. For the co-deposition of PtIr, a binary PtIr-alloy electrolyte was used applying PED. Micrographically, areal micro- and nano-scaled Pt sub-structure were observed, supplemented by homogenously distributed, nanosized Ir agglomerates for the successive PtIr deposition. In contrast, the PtIr co-deposition led to spherical, nanosized PtIr agglomerates. The electrochemical ORR and OER activity showed increased hydrogen desorption peaks for the Pt-deposited substrate, as well as broadening and flattening of the hydrogen desorption peaks for PtIr deposited substrates. The anodic kinetic parameters for the prepared electrodes were found to be higher than those of a polished Ir-disc.

The present study aims to investigate gas diffusion electrodes with ultra‐low platinum loading and increased durability, prepared by pulsed electrodeposition process, applicable for polymer electrolyte membrane fuel cells (PEMFC). Testing was performed both, in situ in a PEMFC test bench while prepared GDEs were compared to anodes and cathodes with commercially available catalysts by Johnson Matthey (JM), as well as ex situ regarding electrochemical properties and catalyst layer structure. High and stable performance of developed electrodes was achieved, while the Pt catalyst loading of investigated anodes and cathodes was reduced to 10 µgPt cm−2. The catalyst deposition was achieved via pulsed electrodeposition process from H2PtCl6‐containing electrolyte on an oxygen plasma‐pretreated corrosion‐stable carbon nanofiber (CNF) support. In situ performance tests show a similar operation behavior of the compared anodes, while activation losses of investigated cathodes are high due to the limited amount of catalyst material. However, Pt/CNF_c cathodes show significantly higher power densities than cathodes prepared with JM catalyst. Membrane electrode assemblies containing developed Pt/CNF_a anodes with 10 µgPt cm−2 reached a power density of 0.525 W cm−2 at a cell potential of 0.65 V, which was similar to anodes with commercially available HiSPEC 2000 catalysts by JM. Accelerated stress tests (AST) revealed that Pt/CNF_a anodes preserve their performance, whereas the commercial catalyst degraded severely. Cyclic voltammetry (CV) indicated a high electrochemical active surface area of Pt/CNF_a anodes. Moreover, the electrode characteristics, analyzed via electrochemical impedance spectroscopy after AST, showed marginal anode degradation.