Abstract
The mechanism of methanol electro‐oxidation is generally discussed on the basis of Horiuti's rate theory, in which the reaction processes under steady‐state conditions are taken into account. Experimental results on Pt‐solid polymer electrolyte (Pt‐SPE) in acidic solutions were analyzed, since steady‐state conditions were found to be attained on Pt‐SPE. In the analysis, the interaction between the adsorbed species was found to be expressed by a linear approximation (Temkin) adsorption isotherm. As a result, adsorbed 
or 
with adsorbed 
or OH, respectively, is suggested to be the intermediate of the reaction under steady‐state conditions; their reaction step is the rate‐determining step (rds). Therefore, adsorbed 
on Pt observed by infrared spectrometry, previously suggested to be a poison for the Pt electrode, is also not considered to be an intermediate of the reaction, while the reaction is at the steady‐state condition. The present analysis is supported by evidence of the absence of a deuterium‐protium exchange reaction between 
and 
; the hydrogen of the methyl group is not released by the preceding steps of the rds.