Abstract
Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.
Highlights
A direct methanol fuel cell (DMFC) is closely related to a polymer electrolyte fuel cell (PEFC)
While the PEFC uses hydrogen gas with enough moisture as the fuel, the DMFC is supplied with a diluted methanol solution
During the occurrence of the methanol oxidation at the anode electrode and the oxygen reduction at the cathode electrode, the electrons are passed through the external circuit and generate electricity
Summary
A direct methanol fuel cell (DMFC) is closely related to a polymer electrolyte fuel cell (PEFC). The DMFC has significant advantages such as high energy density, a system with simple configuration and convenient transportation of fuel due to the use of methanol directly instead of hydrogen. It has received great attention in applications for power supplying systems for mobile or portable devices [1,2,3,4,5,6,7]. Despite the advantages described above, there are several problems such as low methanol oxidation kinetics concerning the use of a large amount of precious metals and methanol crossover from the anode to cathode side through the membrane [8,9,10,11]. Pd is expected to have a good stability with Pt because of their similar valence shell electronic configuration and lattice constant [15,16,17,18]
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