Effect of a carbon support containing large mesopores on the performance of a Pt-Ru-Ni/C catalyst for direct methanol fuel cells

Direct methanol fuel cell (DMFC) catalysts, Pt-Ru-Ni, supported on carbon-containing large mesopores (LMC) or XC-72 carbon black were prepared by a chemical reduction method. The homemade carbon supports were characterized by X-ray diffraction (XRD), BET surface area, and scanning and transmission electron microscopy (TEM). Catalyst performance was tested through polarization and power density curves. Electrochemical impedance spectra of fuel cells were plotted at different cell voltages. The particle size, composition, and micromorphology of Pt-Ru-Ni nanoparticles were determined by XRD, energy dispersive analysis of X-ray (EDAX), and TEM, respectively. The results of physical characterization show that both supports have the same amorphous structure, and the only difference is the BET surface area and pore structure, which play an important role in improving catalyst performance. XRD analysis shows that both catalysts exhibit face-centered cubic structures and have smaller lattice parameters than Pt alone. Their sizes are relatively small, about 4.0 nm, and their size distributions are very homogeneous. The compositions of catalysts on the two different supports are almost the same. A remarkable enhancement in catalytic activity is observed when the Pt-Ru-Ni catalyst was supported on LMC. The main reasons for the significant improved performance of the DMFC are improved diffusion in the catalyst layer and increased utilization of the catalyst.