Effects of ozone treatment of carbon support on the performance of Pt-Ru/C catalysts for direct methanol fuel cell

This research was aimed to increase the utilization of platinum-ruthenium alloy (Pt-Ru) catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The Vulcan XC-72 carbon black supported platinum-ruthenium catalysts were prepared by chemical reduction method. The support was pretreated by ozone at different temperatures and time. The specific surface area of the samples was evaluated by standard BET method. The oxygen concentration in carbon was determined by XPS. It showed that the oxygen concentrations in carbon were decreased and then increased with pretreating time, and specific surface area of carbon was decreased with the time at the same temperatures. The specific surface area of the carbon was increased with increased temperature, and oxygen concentrations in it were decreased and then increased with increased temperature at the same time. Pt-Ru/C catalysts supported on untreated and treated carbons black were characterized and tested for methanol electrooxidation. Transmission electron microscopy and X-ray diffraction were used to characterize the influence of carbon treated with ozone on Pt-Ru/C catalysts. It was found that ozone treatment resulted in a more homogeneous distribution of the Pt-Ru alloy in carbon. In 0.5 mol/L CH3OH and 0.5 mol/L H2SO4 solution, cyclic voltammetry and stationary polarization were used for methanol electrooxidation on Pt-Ru/C catalysts, showing that the catalytic activity of Pt-Ru/C catalysts supported on ozone treated carbon was higher than on untreated one. The effects of time and temperature of ozone treatment on the performance of Pt-Ru/C catalysts were discussed. Electrochemical measurements showed that the catalyst supported on carbon after ozone treatment for 6 min at 140 degrees C had the best performance.