Investigation of methanol oxidation on unsupported platinum electrodes in strong alkali and strong acid

Porous unsupported electrodes are made from platinum powder prepared by a room-temperature NaBH4 reduction method. Cyclic voltammograms (CVs) are recorded in different electrolytes of high and low pH in the presence and the absence of different concentrations of methanol. Various electrochemical processes occurring in different potential regions of the CVs are discussed. Steady-state galvanostatic polarisation measurements for the methanol oxidation reaction (MOR) on these electrodes in different electrolyte/methanol mixtures are also carried out. The MOR performance increases from a highly acidic range to a highly alkaline range. On increasing the KOH concentration above 6 M, however, the activity declines. Also, the MOR performance changes on changing the methanol concentration in a solution of a given pH. The highest MOR activity is obtained in a 6 M KOH+6 M CH3OH mixture. It is concluded that by choosing the proper ratio of OH− ions and CH3OH in solution, it is possible to remove completely the intermediate organic species and/or poisonous species that retard the MOR rate on the electrode surface.