Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene: A highly efficient anodic catalyst for direct formic acid fuel cells

For the first time, Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene (Pd and PdCo/PPI-g-G) are prepared and characterized with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The electrocatalytic activity of Pd and PdCo/PPI-g-G are investigated in terms of formic acid electrooxidation in H2SO4 aqueous solution. The PdCo/PPI-g-G shows much higher formic acid oxidation activities in comparison with Pd/PPI-g-G, and it is more resistant to the surface poisoning. This improved electrocatalytic performance may be due to the fine dispersion of PdCo alloy nanoparticles and bifunctional effect. The kinetic parameters such as charge transfer coefficient and the diffusion coefficient of formic acid are estimated under the quasi steady-state conditions. (C) 2013 Elsevier B.V. All rights reserved.