Effect of OMC and MWNTC support on mass activity of Pd[sbnd]Co catalyst for formic acid electro-oxidation

Abstract

The electrochemical evaluation of PdCo catalyst supported on Ordered Mesoporous Carbon (PdCo/OMC) synthesized by the polyol method is reported in this work. OMC is synthesized via self-assembly in aqueous solution, as an alternative route to conventional preparation methods. The electrocatalytic performance of PdCo/OMC is evaluated for Formic Acid Oxidation Reaction (FAOR). The results are compared with those of PdCo on Multi-Walled Carbon Nanotubes (PdCo/MWCNT) and Pd/OMC, prepared by the same procedure, with the aim to evaluate the effect of support and the Co contribution during the FAOR. The catalysts are characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS). Cyclic voltammetry (CV) and chronoamperometric studies are carried out in acid media with different formic acid concentrations (0.1, 0.5 and 1 mol L−1). According to TEM results, PdCo/OMC exhibits smaller particle size (∼3.5 nm) and enhanced distribution of nanoparticles compared with PdCo/MWCNT. At 0.5 mol L−1 HCOOH, PdCo/OMC delivers a higher anodic mass current density (185 mA mg−1Pd) of the FAOR than PdCo/MWCNT (94.3 mA mg−1 Pd). Moreover, at 1 mol L−1 HCOOH the jf/jb ratio for PdCo/OMC is 1.09 mA mg−1Pd, higher than the ratios determined for PdCo/MWCNT (0.76) and Pd/OMC (0.85). The improvement of the mass catalytic activity of PdCo/OMC is attributed to the combination of the mesoporous structure of the support, which promotes the catalyst-support interaction facilitating the mass transfer process during the reaction, and to the incorporation of Co in the Pd structure.