Investigation of the SMSI Effect on Hydrogen Oxidation Selectivity by Rotating Disk and Floating Gold Electrodes

Degradation of proton exchange membrane fuel cells (PEMFCs) due to start-up/shut-down events, fuel starvation, and catalyst poisoning shortens their lifetime. These degradation mechanisms can be mitigated by developing selective catalysts for the hydrogen oxidation reaction. In this study, we developed a hydrogen oxidation reaction (HOR)-selective Pt/TiO2 catalyst with catalytic properties modified by strong metal–support interaction (SMSI). Scanning transmission electron microscopy showed the presence of a thin TiOx overlayer on the surface of Pt nanoparticles, while X-ray photoelectron spectroscopy showed a negative shift of the Pt4f binding energy. The electrocatalytic properties toward HOR and the oxygen reduction reaction (ORR) were investigated using both a rotating disk electrode (RDE) and a faster mass-transport technique, namely, the floating gold electrode (FGE). Specifically, the FGE measurements allowed us measuring the HOR activity of Pt/TiO2 and Pt/C at relevant current densities and without strong diffusion limitations, which is not possible with RDE. The FGE measurements demonstrated that the HOR activity of Pt/TiO2 was retained up to 1.5 V vs RHE, which is attributed to the SMSI effect. They also revealed lower ORR and HOR mass-specific activities of Pt/TiO2 compared to Pt/C. Nevertheless, SMSI affects more the ORR than HOR, leading to elevated selectivity of Pt/TiO2 vs Pt/C. Below ca. 1000 mA cm–2 on the polarization curve, a PEMFC comprising a Pt//TiO2 anode and a Pt/C cathode showed comparable performance loss after 100 start-up/shut-down cycles than a cell comprising a Pt//C anode and a Pt/C cathode. Above ca. 1000 mA cm–2, a cell comprising a Pt/TiO2 anode and a Pt/C cathode showed improved performance after 100 start-up/shut-down cycles, while a cell comprising a Pt/C anode and a Pt/C cathode showed a slight decay in this region.