Kinetics of Methanol Oxidation on Supported and Unsupported Pt/Ru Catalysts Bonded to PEM

Abstract

The kinetics and mechanism of methanol adsorption and oxidation on real Pt/Ru (1:1) electrodes were investigated. In model electrode systems, the addition of supporting proton‐conducting electrolyte is necessary. Therefore, the influence of sulphuric acid on the kinetics of methanol adsorption and oxidation was also investigated. It turns out that the steady state adsorption is not significantly affected by the addition of sulphuric acid. However, if sulphuric acid is used as an additional electrolyte, the rate of methanol adsorption and steady state oxidation decreases, whereas the active surface of the catalyst increases. The mechanism of methanol oxidation is not affected by the addition of sulphuric acid. At low potentials, the adsorption of methanol is found to be much faster than its oxidation. Hence, the oxidation of the methanol intermediate species is believed to be the rate‐determining step under these conditions. This result is confirmed by apparent orders of reaction of about 0.5. At potentials in the range of 0.3–0.5 V, a mixed activation‐adsorption control is supposed, whereas at potentials more positive than 0.5 V, the adsorption of methanol is probably the rds. This is supported by the apparent reaction orders and apparent activation energies of methanol oxidation.

Carbon supported Ru–Se as methanol tolerant catalysts for DMFC cathodes. Part II: preparation and characterization of MEAs

“…In combined electrochemical and microscopic/spectroscopic investigations (see Figs. [9][10][11][12]15), MEAs made by the CCM method were used. Independent of the GDL or CCM method the catalyst layers were always prepared from catalyst inks using the roll-over knife technique.…”

“…There are several differences between fuel cell operation and RDE experiments: It is well-known that the adsorption of sulfate ions causes a significant loss of performance, even though the utilization of catalyst is enhanced [10,11]. Furthermore, the rate of oxygen transport through sulphuric acid + thin catalyst layer (RDE) or a gas diffusion electrode (MEA), and the oxygen concentration at the active sites may be different.…”

Supported Pt and Pt–Ru catalysts prepared by potentiostatic electrodeposition for methanol electrooxidation

“…It was determined experimentally that CO ads is the most stable product formed during methanol oxidation [37,38], but other adsorbed species such as CH 3 O, -CHOH, and -COOH have also been identified by RMN, DEMS, ECTDMS, and SNIFTIRS [49][50][51][52][53][54]. These are less stable intermediaries that difficult CO diffusion towards OH ads sites.…”

Effect of calcination temperature on electrocatalytic activities of Ti/IrO2 electrodes in methanol aqueous solutions

“…(CO) ads , (COH) ads , (CH 3 O) ads , and (CH 3 OH) ads were all believed as the possible adsorption species [43]. In particular, at low electrode potentials (CO) ads predominately covers on Pt sites [3], causing the poisoning to catalysts.…”