Characteristics of oxygen reduction reaction on Pt cathode modified with Halide ions in direct methanol fuel cell

초록

Oxygen reduction reactions (ORR) on the cathode in direct methanol fuel cell (DMFC) operation are affected by the ability of Pt to electrochemically oxidize methanol reaching it by diffusion from anode. Methanol crossover is still major problem for the commercialization of DMFC, since it leads to a serious decrease in the performance of the cathode, i.e., lower overall fuel cell efficiency. This problem can be overcome by the development of new cathode that is inactive for methanol oxidation. Hydrogen adsorption/desorptions in ORR, are significantly affected by the presence of diffused methanol. With the increase of methanol concentration, higher fraction of Pt cathode was covered with adsorbed intermediate CO and hydrogen adsorption was retarded and its mechanism is also altered. In this work, the effects of methanol on ORR are investigated with the modification of Pt electrode with halide ions and the installation of reference electrode in membrane electrode assembly. The presence of chloride ions inhibits the oxidation of methanol but favors the adsorption of hydrogen ions. Variation of charge transfer resistance in ORR was analyzed with the impedance spectroscopy using dynamic hydrogen electrode.