The loading of Pt-group metals (PGMs) in PEMFCs has been lowered considerably since the first uses
of PEMFCs in the 1960s, by up to two orders of magnitude. The PGM loading still needs to be reduced
to a level comparable to that in current model catalytic converters required for IC engine cars in most
modern industrial states [1]. The U.S. Department of Energy has set a target for PGM loading in
PEMFCs of 125 μg kW^-1 and a total PGM loading of at 125 μg_Pt cm^-2 to be reached by 2020 [2]. Previous
approaches to lower Pt loadings to this level have involved sputtering, electrodeposition, ion-beam
techniques and electro-spray techniques [3].

Here we report a novel method of filter-deposition of highly efficient and high power density Pt/C
catalyst-coated membrane (CCM) layers using commercially available catalysts. Previous efforts in our
research group have demonstrated that using this electrode deposition method in combination with
the floating electrode technique allows kinetic measurements of hydrogen oxidation and oxygen
reduction across the full fuel cell potential window without a mass-transport limitation [4]. We show
that using a modified form of this filter-deposition method we can fabricate low-loading electrodes
with high Pt utilization compared to commercial CCMs and other literature reports.

Electrodes were deposited with loadings between 20 μg_Pt cm^-2 and 100 μg_Pt cm^-2 by filtration of catalyst
inks (60 wt.% Pt/C) through a track-etched polycarbonate (PCTE) membrane, hot-pressing to a Nafion
membrane, dissolution of the PCTE membrane in alkaline solution and finally re-acidification of the
Nafion membrane in 1 M H₂SO₄. A new method of electrode break-in was developed which allowed
increases in mass activity of up to three times compared to the more commonly used DoE method.
PEMFC single cell tests showed that the lowest loading electrodes had performance exceeding that of
DoE targets with 82 μg_Pt kW^-1 with a total loading of 20 μg_Pt cm^-2. Increasing the total electrode loading
to 100 μg_Pt cm^-2 gave a catalyst to power ratio of 128 μg kW^-1, almost matching the DoE requirement
without the need for high performance alloy catalysts.

This method of CCM manufacture seems very promising at creating thin, evenly-distributed, highperformance catalyst layers in a simple and reproducible manner and has potential to gain even more
performance with optimised catalysts and ionomer/carbon ratios.

References
[1] A. Kongkanand, N. P. Subramanian, Y. Yu, Z. Liu, H. Igarashi, and D. A. Muller, “Achieving High-Power
PEM Fuel Cell Performance with an Ultralow- Pt-Content Core−Shell Catalyst,” ACS Catal., vol. 6, pp.
1578–1583, 2016.
[2] US DoE, “Multi-Year Research, Development, and Demonstration Plan” Fuel Cell Technologies Office,
Washington DC, 2013.
[3] B. N. Popov, “Development of Ultra-low Doped-Pt Cathode Catalysts for PEM Fuel Cells (PHASE II),” in
2015 DOE Hydrogen and Fuel Cells Program Review Development, 2015.
[4] C. M. Zalitis et al., “Electrocatalytic performance of fuel cell reactions at low catalyst loading and high
mass transport,” Phys. Chem. Chem. Phys., vol. 15, no. 12, p. 4329, 2013.

Figure 1. (a) SEM cross-section of an electrode with 10 ug_Pt cm^-2 with inset view of the catalyst layer, (b) photograph of an as-prepared CCM with a loading of 10 ug_Pt cm^-2