I have several question regarding the MOR; hope anyone help me better understand.
1- in CV using (KOH+MEOH) what is the indication of absence of the redox peaks? shouldn't they exist as a sign that the electrode is being regenerated and able to carry the MOR?
2-why some papers don't operate in potential windows to reach the Methanol Oxidation peak and they use the onset potential as an indication to MOR? isn't important to know where the peak is?
3- what is the indication of the area under curve in Cyclic voltammetry (large vs small) for both (KOH alone) and (KOH+Methanol)
any resources are very appreciated.
Thank you.
1-2. The MeOH concentration is too high to see the peak
3 What is the CV of KOH alone?
@Yurii V Geletii
Could you further elaborate, why the high concentration would result in peak absence? My question was when the potential window is 0V -0.6V shouldn't the peak start at about 0.75V.? The scan rate doesn't even reach the voltage of the peak.
3. The area of the activation curves of the material in KOH before the addition of Methanol (large vs small)
I'm confused by your questions. Do you use aqueous solutions or KOH in MeOH? What are the concentration? ref and working electrode?
Chandan Kumar Tiwari, Yurii V Geletii
RE is Ag/AgCl, CE is Pt wire, WE is glassy carbon.
CV measurements were carried in 1M KOH and in (1M KOH + 0.5M Methanol)
we first carry an activation step in KOH alone and then we measure the MOR in (KOH+Methanol)
I experience a peak absence after the addition of Methanol, like the following pics. what does it mean?
I'm asking about the indication of obtaining a large vs small CV curve in the activation in KOH alone
Your instrument has different sensitivity in these two experiments. Overlay the CVs using the same Y-scale. I see the peak at around 0.3 V on red curves. The peak does not disappear in the presence of MeOH. You have either impurities in you KOH/water solution or your electrode is not well cleaned.
Generaly, the absence of peak means that methanol is not electrochemically active under the conditions of your experiment such as potentials window, scanning speed, pH, temperature...
A couple ideas:
(1) Methanol oxidation typically requires an electrocatalyst to adsorb the various intermediates along the reaction pathway. Glassy carbon is relatively inactive in this regard. So much that it is typically used as an "inert" conductive backing material upon which more active materials (such as Pt/C nanoparticles) may be deposited. Transition metals such as platinum, palladium, to a certain extent gold (in alkaline media), iridium, etc, are examples of electrode materials that can catalyze the oxidation of methanol (to either CO2 other incomplete oxidation products such as formaldehyde and formic acid) at an appreciable rate.
(2) That said, glassy carbon may still be able to oxidize methanol to some extent, just likely at a much lower rate than the transition metals I listed above. The oxidation of methanol on most of those metals does not occur at an appreciable rate until you apply > 0.6 V vs. RHE. If I were you I would make my voltage window from 0 to 1.2 V vs. RHE and check for peaks in that range. Make note that since you are using a Ag/AgCl reference in base, you need to account for the pH shift of the reference electrode potential. For example, if your Ag/AgCl records ~ + 0.20 V vs. SHE, then the potential which corresponds to 0 V vs. RHE would be (-0.20V) + (-0.059*pH) ~ (-0.20 - (-0.059*13) = -0.967 V vs. Ag/AgCl. You could also make an RHE (bubble H2 over a Pt wire), put it in your electrolyte, and measure the OCP of the RHE vs. your Ag/AgCl in the same electrolyte to measure the Ag/AgCl potential directly. Check this post for more details (https://www.researchgate.net/post/How_to_convert_a_potential_collected_with_reference_to_Ag_AgCl_to_Reversible_Hydrogen_Electrode2)
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