Improvement of the sputtered platinum utilization in proton exchange membrane fuel cells using plasma-based carbon nanofibres

Proton exchange membrane fuel cells are complex nanostructures containing a catalyst (usually platinum), proton and electron conductors and pores. Their electrode performance is strongly influenced by the size, the repartition and the orientation of the nanoseparated materials used and the pores. This paper investigates the electrical performance achieved by three designs of plasma-prepared Pt/C electrodes with low Pt loadings (from 0.01 to 0.1 mg(Pt) cm(-2)). A plasma sputtering process was used for the synthesis of Pt nano-clusters in three different microporous supports: a single oriented layer based on aligned carbon nanofibres (CNFs, custom-made by plasma), a single convoluted layer based on Vulcan carbon particles (LT1600, known as a gas diffusion layer-GDL) or a double layer composed of CNFs covering a GDL. Membrane electrode assemblies (MEAs) were prepared by hot-pressing one of these three electrodes with a commercial electrode (0.5 mg(Pt) cm(-2)) and a commercial Nafion 115 membrane, and compared with a reference MEA (from Electrochem Inc. with a Pt loading per electrode of 0.5 mg(Pt) cm(-2) and a maximum power density of 425 mW cm(-2)). The cathodic Pt utilization efficiency in the best performing plasma-prepared cathode (based on the double layer GDL/CNF) with a Pt loading of 0.1 mg(Pt) cm(-2) is 3.6 times higher than that measured for the commercial cathode (3.1 versus 0.85 kW g(Pt)(-1)). On the anode side, the three designs of plasma-prepared electrodes with 0.01 mg(Pt) cm(-2) lead to similar MEA performance than a commercial electrode at high backpressure (3 bar). At a lower backpressure, the GDL/CNF electrode is the best performing plasma-prepared anode.