I record ORR by RDE method. My the current density for ORR usually ranges 4-5 mA/cm2 at 1600 rpm in acid or basic electrolyte. However, the current density appears near 6 at mA/cm2 at 1600 rpm in some good papers. I want to try to get tha same current density with those papers. What is wrong with my experiment? Please tell me some comments on it. Which flow rate of oxygen during measurement is suitable?
The diffusion current depends on the geometrical area of your electrode. The bigger the area, the higher diffusion current density. Thus, unless you actually make the geometrical area of your electrode bigger, there is nothing you can do about it
Geometrical surface area of the Pt/C electrode is the main factor. I think the particle size of Pt in your electrode is larger than those used by others.
How is your Pt/C article size? probably your problem is related with the particle size of your material. For a good density current, the particle size is lower than 3 nm.
the particle size does not influence you diffusion current. Look at the Levich equation, only the geometrical area of the electrode is a factor
The smaller the particle size, the geometrical surface area of the electrode is higher. So particle size has relation with the achieved current density. One more thing is the size of the support C. The smaller size of support enables to obtain smaller size of Pt.
You should carefully read Yannick Garsany's papers on measuring ORR, they are excellent guides for best practices for ORR measurement. In my experience, the quality of ink film on the RDE has huge influence on the ORR and obtainable limiting currents. Also, I believe that extremely low Pt loadings might also lower the limiting current. Are you using HClO4 or H2SO4 electrolyte?
https://www.researchgate.net/profile/Yannick_Garsany
Hello everybody,
First of all, thank you very much for your valuable contributions to my study. I have been reading Yannick Garsany`s papers carefully. Thus, I have some points to clarify. In the Garsany`s paper, they mentioned that "Any gas bubbles attached to the working electrode surface were dislodged by rotation at > 3600 rpm." In my case, I have an electrode which is allowed to rotate at maximum 2500 rpm. How could I dislodge the bubbles attached on the electrode surface in another way? Second, how could I clean well the teflon cell? Usually, I use the teflon cell in case of alkaline electrolyte. Third, I want to find out a more clear picture of RHE for safe working with it. If anybody has it, please share it? Finally, thank you again.
You cannot literally compare your number with ones on the papers. You have to think in relative terms, instead. The good papers you referred to must have an internal reference, i.e. a commercial catalyst that you can also buy or already have. Find out how much their catalyst is better than their reference and compare yours with your reference. After that, you can follow all the suggestions that have been made thus far.
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