Oxygen Reduction Reaction Activity Improvement in Cu/PtPd Nanocatalyst Based on Core-Shell Structured through Electrochemical Synthesis on Porous Gas Diffusion Electrodes in Polymer Electrolyte Membrane Fuel Cells

摘要

In this paper, a two-step method is developed for efficient preparation of Cu/Pt-Pd core-shell structured catalyst on Nafion-bonded carbon paper electrodes for a polymer electrolyte membrane fuel cell. Copper nanoparticles with diameter distribution of 80-160 nm are obtained by potential-modulation electrodeposition. In copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. After the copper electrodeposition the replacement of Cu by PtPd occurs spontaneously by an irreversible redox process. The nature and composition of PtPd/Cu on pretreated carbon paper are characterized by field emission-scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The as prepared Cu/PtPd electrode is found in the form of core-shell structure with uniform dispersion on the surface with average nanoparticles of 41.5 nm diameter. Electrochemical activity of PtPd/Cu and conventional Pt/C on pretreated carbon paper electrodes towards oxygen reduction is studied by linear sweep voltammetry experiments. Low values of Tafel slope and free activation energy reveal that Cu/PtPd with core-shell structure shows greater electrochemical activity than conventional Pt/C catalyst. Electrochemical surface area (ECSA) results also show that Cu/PtPd with core-shell structure has greater stability than the Pt/C electrode.