2004 Volume 53 Issue 10 Pages 1055-1059
We have studied the influence of Cl−ion for methanol electrooxidation in direct methanol fuel cells (DMFCs) by using a Nafion-modified Pt microelectrode(φ 50 μm). The microelectrode was employed to form a uniform-thick Nafion overlayer on the Pt surface. Hg/Hg2SO4 and Pt wire were used as a reference and a counter electrode, respectively. Current-potential curves were measured in a 0.5 M H2SO4 or 0.5 M CH3OH + 0.5 M H2SO4 solution. KCl was added into the solution at arbitrary rates. As a result, we have observed that (i)Cl−ion adsorbs on the Pt surface, which prohibited not only Pt oxide formation but also Methanol electrooxidation. The Nafion membrane prevented Cl−adsorption, because of it’s cation exchange property. (ii)However, a small part of Cl−ion was able to pass throughout Nafion membrane and adsorbs on the Pt surface. (iii) It has been known that a strong correlation exists between Pt surface oxide formation and methanol electrooxidation at a Pt electrode.
