Carbon monoxide and methanol oxidation on potential-modified Pt-Ru/C electrocatalyst for polymer electrolyte fuel cells

In this paper, the effect of the anodic treatment of carbon-supported Pt-Ru nanoparticles using a HP 20% 1:1 Pt-Ru alloy on Vulcan XC-72 carbon black on the CO stripping and methanol oxidation reaction (MOR) has been analyzed. Thin-layer electrodes were prepared by depositing catalyst inks of Pt-Ru/C and Nafion on glassy carbon (GC) disks. Steady-state polarization at potentials >1.00 V vs. RHE in 0.5 M H₂SO₄ was used for the electrochemical activation of the specimen. Cyclic voltammetry was applied for electrochemical testing. The morphological analysis was performed by transmission electron microscopy (TEM), energy dispersive X-ray (EDX), selected-area electron diffraction (SAED), and Fast Fourier Transform (FFT). The present results showed that the anodic potential treatment causes Ru segregation with some carbon oxidation and agglomeration of nanoparticles. Activation of CO and methanol oxidation was found, indicating the production of the beneficial hydrous Ru oxide, RuO_xH_y, the promoting species for both reactions. For the MOR, the optimum potential of anodic treatment was located at 1.40-1.60 V. An apparent double Tafel slope behavior with values of 120 and 200 mV dec^-1 was obtained after this optimum potential treatment, which was tentatively attributed to the existence of two different active sites for the MOR.