Optimization of Pt Catalyst for Anode/Cathode of PEMFC via Magnetron Sputtering

Wednesday, 4 October 2017: 10:40
National Harbor 2 (Gaylord National Resort and Convention Center)
A. Ostroverkh, M. Dubau, V. Johanek, P. Kus (Charles University), I. Khalakhan (Charles Univeristy), M. Vaclavu (Charles University), R. Fiala (Central European Research Infrastructure Consortium), Y. Ostroverkh, and V. Matolin (Charles University)
In this study, the performance of the thin film Pt catalyst with loading in the range of 1–200 µg/cm2 prepared by magnetron sputtering was investigated for both anode and cathode sides of a proton exchange membrane fuel cell (PEMFC) in H2/O2 and H2/air modes (see example of anode study in Fig.1). Standard microporous layers comprising carbon nanoparticles and Teflon PTFE and FEP supported gas diffusion layer, as well as their modifications by magnetron deposition of carbon in N2 atmosphere (leading to CNx) followed by plasma etching were used as substrates for Pt deposition (Fig.1 right).

The choice of CNinterlayer was motivated by the higher resistance of the CNx structure as compared to pure C which was determined by a mass-spectrometry analysis of PEMFC exhaust at different cell potentials. Benefits of lower absolute carbon etching rate and at least 0.25 V lower corrosion threshold were found for CNxon both sides of the PEMFC (see Fig. 2 for cathode results).

The anode catalysts with various Pt loadings on all the substrates were tested and compared with a standard state-of-the-art commercial Pt/C reference anode with respect to their efficiency for hydrogen oxidation reaction (HOR; see Fig. 1). Performance up to 1.3 W/cm2 in pure H2 and O2 was achieved for anodes containing Pt loading of 2–10 µg/cm2 on CNsubstrate. It is comparable to the performance of a standard commercial Pt/C anode with loadings 200–400 µg/cm2.

The same experiments as for HOR were performed for and oxygen reduction reaction (ORR). In this саsе, cathodes with various Pt loadings were tested. The maximum performance up to 0.54 W/cm2 in pure H2 and O2 was found for cathodes with Pt loadings in the range of 20–100 µg/cm2. The Pt loading of 100 µg/cm2 was found as the limit thickness for the magnetron sputtered thin film, further increase of Pt content leads to efficiency decrease of PEMFC. When PEMFC is switched from H2/O2 to the H2/air, the power is decreased 2.0 to 2.2-times relative to the reference Pt/C powder electrodes and 2.8 to 3.0-times on thin film Pt electrodes.

We have also performed 450-hour durability tests in a pulsed regime of 30min open voltage + 30 min under 400 mA/cm2 load, as well as in the regime of stable 400 mA/cm2load for both anode and cathode sides of the PEMFC with Pt loadings of 2 µg/cm2 and 20 µg/cm2.

Based on our research, the PEMFC with best Pt utilization was found for MEA based on a combination of anode with 2 µg Pt per cm2 and cathode with 10 µg Pt per cm2, yielding the total power density 0.45 W/cm2 for as little as 12 µg/cm2 of total noble metal content.