Abstract From the several experiments described above, it can be concluded that the electroactive species in the anodic reaction of methanol in the moderate potential range is the methylate anion only. The evidence for this conclusion will be summarized below. The static potential of the platinized platinum electrode in absolute methanol is affected by the methylate concentration. It is confirmed that a definite transition time in an anodic chronopotentiogram is observed only for the case of the methylate ion. The results from the potentiostatic experiments also support this conclusion. Although this is the case, methanol is still electrolyzed to form formaldehyde at a higher potential range. Product analysis shows that the yield of formaldehyde is affected appreciably by the kind of supporting electrolyte. Except fluorine, an appreciable number of free halogen molecules is detected in the solution after electrolysis. Even in the case of an iodine/iodide couple, the thermodynamic potential is far more positive than that of methanol. It may be understood from this fact that the electrooxidation of neutral methanol is strongly irreversible. Furthermore, it seems quite plausible that some part of the methanol is decomposed by the attack of the free radicals (or atoms) formed by the discharge of salt anion. The reaction scheme can be formulated as follows: X− → X+e X+CH3OH → HX+CH3O (or CH2OH) 2CH3O (or CH2OH) → CH3OH+HCHO Coinciding with this hypothesis, the current efficiencies of formaldehyde formation are increased in the order of the hydrogen-abstracting power of the four halogen atoms examined, i.e.,I<Br<Cl<F (see Fig. 9). The mechanism of the electrolytic oxidation of methanol in aqueous solution has been studied by many authors, but no mechanism has yet been accepted without any ambiguity. The static electrode potential observed in an aqueous methanol solution rests near the thermodynamic redox couple: CH3OH=HCHO+2H++2e 0.23 V . NHE It is evident, however, that the real process does not proceed through such a simple reversible path. Another mechanism proposed is the catalytic dehydrogenation: CH3OH=HCHO+2H(Ads) 2H(Ads) → 2H++2e This mechanism seems somewhat plausible, and some indirect evidence for it has been pointed out by the present authors.12) Although it is difficult to state a definite conclusion about the reaction mechanism in the aqueous solution, the present conclusion, emphasizing the importance of the methylate ion, seems applicable in the case of the aqueous phase reaction. The fact that the performance of the methanol fuel cell in the alkaline medium is superior to that in the acidic one can thus be understood if the following reaction is taken into account: CH3OH+OH−=CH3O−+H2O