In my case platinum nanostructure shows lower electrocatalytic activity for methanol oxidation in acidic condition than basic condition. Both current density and stability (i vs t ) decreases in acidic condition than basic condition.. what may be the reason?
i think may be in acidic condition, surface of the nanoparticle are passivated by proton
Till now for PEMFCs, Nafion is widely used membrane for better proton conduction (although serious research is being focused to replace costliest Nafion). Hence an MOR catalyst should be reasonably stable in acidic medium. Hence it is pertinent to stabilse your Pt Nps with topographic and support modifications.
Dear Soumen,
If you ask this, perhaps you should be read more about methanol electrooxidation. First, Pt is not the best catalyst for MOR, actually Pt base alloys (Ru, Sn...) shows the higher performance than single metal. However, Pt is the only one which causes the break on C-H bonds (obviously, reactive intermediates are produces).
Mechanistically, in base media is more efficient than acidic one. Although depends which one is the acid electrolyte. HClO4, H2SO4, H3PO4 has not the same performance for methanol electrooxidation over Pt. Also, is not the same NaOH than KOH. I invite you to discover why, probably you has reading papers enough to know it, just need collect data from them in same blackboard and extract your onw conclusions.
So, first, try to understand which mechanism happens in each, acidic and basic media. After, why co-catalyst (Ru, Sn, oxophylic metals) make Pt more efficient in acidic. And finally, why Pt (or alloy) works better in one mineral acid than other.
Has a huge bibliography talking about where you can find the reason. If you have a more specific question which not find answer, no hesitate ask again.
Regards
Ok, Soumen.
Ask yourself these questions:
What is the mechanism in case of methanol deprotonation in Pt electrode, in general?
What´s happens in H2SO4? I mean, if you introduce Pt on such acid and made you experiments, the electrolite has any influence in? (concentration, adsorption, for instance wich affects to performance)
When KOH is used, which differences can you find in electrode to work differently on H+ or OH-? CO peak appears at same potential? Why? also clean surface CVs are quite similar?
As you see, has too many factor to keep in mind. However, no worries, it is not difficult, just need to get overall information to reach to any conclusion.
I guess you wont perform a single DMFC cell, with nafion in alkaline media. Only three electrode experiments. So, take care in select good counterelectrode and reference electrode.
Regards
in acidic medium as you have mentioned that you are using sulphuric acid, HSO4- ions adsorb on the surface of the catalyst. when you introduce methanol on the electrolyte methanol has to first replace the adsorbed ions and get oxidised. probably in your case the morphology of the Pt nanostructure is influencing this process. so plz mention what is the structure. whereas in basic medium the OH- ion itself gets adsorbed and desorbed in the MOR potential window. so it gives higher current density
Thank you Manjeet. I have porous structure of Pt, made from the assembly of Pt NWs. can you suggest any paper related to your information?
waiting for a reply.
As you are working on MOR activity of Nanowires, i would say please follow
1) http://pubs.acs.org/doi/abs/10.1021/ja402955t
2) http://onlinelibrary.wiley.com/doi/10.1002/anie.201303035/abstract
please see the supporting info and have someideas on the MOR activity.
i would suggest you to do your MOR in acidic medium only because till now PEMFC is operated in acidic medium in a commercial scale as also sugessted by Ananda Ganesh.
so as far as variation in acidic medium is concerned you can read the attached file. infact i too am working on the same front. so i would be happy to share and discuss the ideas on this. keep going brother. all the best
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