Bimetallic electrocatalysts (Pt-M) supported on single-wall carbon nanotubes for hydrogen and methanol electrooxidation in fuel cells

Abstract

[EN] A series of Pt-Ru and Pt-Mo bimetallic catalysts were prepared via a chemical reduction method by bubbling CO to form carbonyl compounds as metal precursors. In both cases the Pt-Ru and Pt-Mo bimetallic electrocatalysts achieved the maximum activity when the amount of Ru and Mo in the material was 50%wt. The physicochemical characterization of the electrocatalytic materials through X-ray diffraction (XRD) and transmission electron microscopy (TEM) has determined the presence of bimetallic structures. The electrochemical characterization using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and polarization curves in Proton Exchange Membrane Fuel Cells (PEMFC) and Direct Methanol Fuel Cell (DMFC) allowed to systematically investigate the electrocatalytic activity of the synthesized materials for the electrooxidation of hydrogen and methanol. The Pt-Ru/SWCNT electrocatalysts showed a higher current density at least 7-fold and 3-fold compared with Pt/SWCNT and Pt-Mo/SWCNT electrocatalysts, respectively. Besides, the Pt50%-Ru50%/SWCNT exhibited a shifting to negative values in the onset potential reaction for the electrooxidation of methanol of 200 mV in comparison with Pt100%/SWCNT and Pt50%-Mo50%/SWCNT electrocatalysts. The experimental and simulated polarization curves obtained from DMFC show that Pt-Ru/SWCNT and Pt-Mo/SWCNT electrocatalysts exhibited higher power and current densities values compared with the Pt/SWCNT electrocatalyst. The membrane-electrode assembly (MEA) with Nafion and the Pt-Ru/SWCNT electrocatalysts showed an open-circuit voltage value of 0.730 V, significantly higher than that the values for the MEAs with Pt/SWCNT (0.663 V) and Pt-Mo/ SWCNT (0.633 V), respectively.