Hi,
When we perform an electrochemical oxygen reduction reaction, should it be a positive-going RDE scan or a negative-going RDE scan?
Thanks,
Saurav
Normally, you should scan from the potential (vs. ref electrode) at which you don't observe ORR (more positive potential than the onset of ORR) towards the potential where you reach a current plateau (mass transport limitied current).
Thank You for your answer. I believe in the same convention as you suggested but the reviewer has argued that the reverse (positive-going) scan is the acutal convention that must be followed.
Hi Saurav,
I am going to take a guess as to what the reviewer is asking and where the confusion maybe coming from. When ORR is performed, you go in the negative direction of the OCV (=cathodic sweep) and then you reverse by going more positive (= anodic sweep). You can repeat this process many times. You would notice that, at least for Pt, the anodic sweep is better than the cathodic sweep (the reason is that by going low potential you reduce the surface oxides and you get a better catalytic surface for ORR). The common practice in the literature is to report the "anodic" sweep. I suspect the reviewer is asking you to show the anodic sweep and not the cathodic sweep.
Best,
Arman
Hi Arman Bonakdarpour Sir,
Thank You for your reply. When we perform an anodic sweep we are not doing ORR and hence presenting that as an ORR data won't be correct..right?
Thanks,
Saurav
Hi Saurav,
You do ORR in both directions, but anodic sweep has lower overpotentials. See Figure 11 in the attached file. All the ORR curves are for anodic sweep, except 1600 RPM, where both cathodic and anodic sweeps are shown. Let me know if this is not clear.
Best,
Arman
Hi Arman Sir,
Thank You for the reference and detailed description.
1) What I understand is that the anodic sweep has to be presented only for noble metal-based compounds or is it applicable for all compounds?
2) In this case, what should be the half-wave potential? Is it for Anodic sweep? cathodic sweep or the average?
Thanks,
Saurav
Hi Saurav,
You are correct, for Pt-based catalysts, anodic sweep is certainly preferred. For non-noble metal catalysts, however, cathodic sweep would appear to be better so it may be preferred. The most important thing is to indicate which direction you are using and be consistent, both in your work and if possible with literature which you may compare. If you have several rotation speeds, it would be good to show one of them in both anodic/cathodic directions. You can use half-wave potential for either one. I would not use the average, again unless you are comparing with other work which followed the same procedure.
Best,
Arman
- Badges
- Science topic
- Similar topics
- Chemistry
- Electrochemistry