in most of the alcohol (methanol, ethanol) oxidation papers the medium used is acidic. i have seen only few papers in basic medium. what is the specialty in acidic medium or is a challenge to oxidize in acid? In basic medium also mostly KOH very few are from NaOH. Please anyone explain about the principle and mechanism behind this. thanks in advance..
There are probably several reasons. Traditional PEM fuel cells are more popular than alkaline fuel cells, so therefore there are more papers on electrocatalysts for traditional PEM fuel cells, but there are quite a few studies of alcohol oxidation in alkaline media, especially non-platinum group metal catalysts which work pretty well in alkaline media..
One of the main reasons that quite a bit of work has been done in acidic conditions is due to the fact that membranes for PEM fuel cells are "proton-exchange membranes" and thus work best in acidic conditions. In recent years, alkaline membranes have been developed and are slowly being introduced...
Thanks for your answer Shelley & Daniela mam, i have red some papers with the same catalyst which works in both acidic and basic medium so that is also possible??. One more thing i would like to ask is in basic medium, is there any change in the catalytic activity in different bases like NaOH and KOH or both are working same?.
Yes, there are catalysts that will work well in both alkaline an acidic conditions... some indeed work better in base. Cations in solution have been shown to have an effect in reactions such as oxygen reduction, hydrogen oxidation or that of alcohols.... for example this paper shows the effect on Pt electrodes: doi:10.1038/nchem.330 How significant the effect is depends greatly on the nature of your catalyst... In some cases the difference between K+ and Na+ might not be too great, but it does seem to be generally thought that K has less of an adverse effect than Na.
Thanks for your information Daniela mam.. i would like to know one more thing, can i conclude the CO poisoning is more in acidic medium compare to alkaline medium?, because after reading some articles i noticed this, the reverse sweep is very intense in acidic medium compare to alkaline. please explain about the principle behind this or please give me some useful links to get information about that thanks.
I'm not sure... I think it depends on the electrode how the pH will affect CO poisoning...
Alcohols are not oxidized by NaOH or KOH, only in an acidic medium such as CrO3 / sulfuric acid or with pyridine chlorochromate. Alcohols such as methyl and ethyl is treated with NaOH or KOH in the transesterification of triglycerides to produce biodiesel.
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