Enhanced CO Tolerance with PtRuAuPd/C Anode Catalyst in Proton Exchange Membrane Fuel Cells

Platinum poisoning in the presence of even trace amounts of carbon monoxide (CO) within a hydrogen fuel degrades the activity of a proton exchange membrane (PEM) fuel cell. Herein, we report a quadmetallic alloy, PtRuAuPd/C, prepared by a water-in-oil microemulsion method for CO tolerant hydrogen oxidation reaction (HOR). The obtained spherical nanoparticles were 3.4 ± 0.5 nm in size with a Pt:Ru:Au:Pd atomic ratio of 22:34:22:22. The X-ray diffraction confirmed the alloy formation through a shift in the Pt peaks. The compositions and oxidation states were elucidated via X-ray photoelectron spectroscopy. The comparison catalysts, PtRu/C, PtRuAu/C, and PtRuPd/C alloys, were also similarly prepared and analyzed. Among all these alloys, PtRuAuPd/C demonstrated the highest electrochemically active surface area of 123.2 m2/g and a CO oxidation peak potential merely 20 mV higher than the PtRu/C catalyst, as measured using CO stripping voltammetry in a 0.5 M H2SO4 electrolyte. The evaluation of CO tolerance through a 30 s exposure to 5% CO at a constant potential revealed PtRuAuPd/C recovery of 93.6% in HOR current density outperforming PtRu/C at 91.5%. Following the durability test cycling, wherein a reduction in surface Ru concentration was observed through cyclic voltammetry, the CO oxidation potential of PtRuAuPd/C remained unchanged, while that of PtRu/C significantly shifted to higher potentials by 270 mV. Single fuel cell assessments at 70 °C revealed higher cell performance of PtRuAuPd/C with pure H2 fuel and higher oscillating potentials during self-oxidation with 80 ppm of CO contamination in comparison to commercial PtRu/C catalyst demonstrating its high CO tolerance.