A.c.-impedance spectroscopy study of oxygen reduction at Nafion� coated gas-diffusion electrodes in sulphuric acid: Teflon loading and methanol cross-over effects

Hydrophobic effect of PTFE‐modified Ru0.3Ti0.7O2electrodes on oxygen evolution in alkaline solution

“…The modification of PTFE onto the Ru o .3Ti o 7 O 2 electrodes obviously affected the evolution behavior. The result resembles that of oxygen reduction on the Pt/C electrode presented by T. Maoka [5]. The electrode containing 30 wt% had the minimum Tafel slope value on oxygen reduction.…”

DMFCs: From Fundamental Aspects to Technology Development

“…The electrochemical methods used for such investigation mainly include steady-state galvanostatic polarizations, cyclic voltammetry and electrochemical transients (chronoamperometry, chronopotentiometry) [4±8, 18±23]. AC-impedance spectroscopy has been used to a minor extent [24]. In general, electrokinetic parameters, i.e.…”

“…In the case of Ru/carbon at high potentials, the surface is mainly covered by Ru oxides which the chemisorption of methanol is hampered [131]. In a previous study [24], it was shown that in the presence of methanol, the Tafel slope for oxygen reduction at 60 C on a Pt surface is practically unaltered at high potentials (±60 mV/dec), i.e. in the region where the surface is composed mainly of Pt-oxides (Fig.…”

“…At lower potentials, where the metallic surface is exposed, methanol is effectively oxidized in the presence of oxygen (Fig. 6); this parasitic reaction causes an increase in Tafel slope from 130 to 170 mV/dec [24]. This effect is the same as that observed in the classical cyclic voltammetry of methanol at Pt electrodes [18]; the methanol oxidation peak in the anodic scan is followed by a sharp decrease in the current due to the formation of a strong Pt-oxide layer on the surface before oxygen evolution.…”

Performance of sputter-deposited platinum cathodes with Nafion and carbon loading for direct methanol fuel cells

“…These included the premixing of ionomer before the loading of the catalyst layer [2][3][4][5][6], Pt loading onto the carbon particles [7,8] and the reduction of Pt particle size by electrodeposition [9][10][11][12][13][14] and sputter-deposition [1,[15][16][17][18] onto the membrane and the carbon substrate were reported. Mass activities were, however, insufficiently obtained although these trials were attempted.…”