Investigation of Carbon Nanofiber-supported Electrocatalysts with Ultra-low Platinum Loading for the Use in PEM Fuel Cells

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 mu g(Pt)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 mu g(Pt) 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 HiSPEC2000 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.