Inhibition of CH3OH oxidation on Pt cathode by chemsorbed Cl-

초록

In the operation of direct methanol fuel cell, methanol (CH3OH) crossover through membrane electrode assembly has been considered as most significant problems. In the oxidation of transport CH3OH on Pt cathode, carbon monoxide is released at the same time as the evolution of CO2 and even in the smallest concentrations, this acts as an extremely efficient poison for fuel cells and renders them inoperative. Of late, new cathode with appropriate composition ratio of Pt and Ru is thus using in order to completely oxidize CO and recover cathodic activity for the reduction of oxygen. In this work, we tried to find new chemisorbed material to inhibit CH3OH oxidation on Pt surface. Analyzing cyclic voltammetry of Pt electrode in CH3OH and sulfuric acid solution in presence of chloride ions, we obtained that the oxidation current of CH3OH was significantly decreased due to chemisorbed Cl-. On the other hand, the underpotential deposition current of hydrogen was maintained and the reduction of oxygen was a little hindered by chemisorbed Cl-. According to the experimental observations, we expect that thinner membrane to allow CH3OH crossover might results in less mass transfer loss and thus, relatively higher concentration of CH3OH could be used.