Electrochemical Behavior of Pt Nanoparticles Supported on Meso- and Microporous Carbons for Fuel Cells

Porous structure of the electrocatalyst support is of importance for mass transfer of reactants and products in electrochemical reactions of fuel cells. This study reports the comparative investigation of the electrochemical performance of Pt nanoparticles supported on the meso- and microporous carbons as well as commercial Pt catalyst E-TEK (40 wt % Pt loading) for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in fuel cells, Ordered mesoporous carbon (OM C) synthesized using the template method was employed as the representative of mesoporous carbon, and carbon black BP2000 was used as the microporous carbon because of Us microporous structure with a high surface area comparable to that of OMC. The samples were characterized by nitrogen adsorption, X-ray diffraction, small-angle X-ray scattering, thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that, for M OR, the Pt/OMC catalyst possessed a significantly higher catalytic activity measured by cyclic voltammetry than that of Pt/BP2000 and its performance even exceeded that of commercial catalyst E-TEK. The electrochemical impedance measurement indicated that Pt/OMC has a smaller charge-transfer resistance and faster overall MOR rate than both Pt/BP2000 and E-TEK catalysts. In contrast, for ORR, the mass activity of Pt/BP2000 is higher than that of Pt/OMC on a rotating disk electrode but comparable to that of E-TEK. The study may suggest that the mesoporous structure of the carbon support is important for liquid-phase electrochemical reactions, while micropores are more suitable for gas reactions at the electrodes of fuel cells. This work would be helpful in understanding the molecular transport of reactants and products in the pore nanostructure of carbon-supported Pt electrocatalysts for fuel cell application.