During the hydrodynamic linear sweep voltammetry of the oxides, I am seeing the decrease in current with increase in rotation speed . what is the reason ?? how to interpret it??
May be you materials is falling of your working electrode.
It is Fe-Co oxide."block the surface"??. i have coated it on the surface of GC electrode.I am studying the ORR catalysis property.
I think you are reaching a steady state, when there's no convection rotating speed very low, the diffusion is mainly planar and a lot of the electroactive species are in the surface of the electrode as you increase the rotation speed you are letting small quantities of your electroactive species reached the electrode surface since this I think you are reaching a steady state and I think you can see it if you are getting a plateu instead of the classic waves.
Let me know if that help you.
Cesar
there is no plateau..U-shaped curves. but just the inverse trend..rpm i chose were 400,800,1200,1600,2000,2400...
can u say other reasons for such behaviour ??
DIsha can you send an image of the voltammetry you are getting, the other reason I can think is that you may have kinetics affecting the measurement. It would be nice to see those voltammetries so I can see what's happening.
Best
thanks Cesar .. actually i conducted experiments once more ..now the results are good..i think may be the oxygen supply was not proper before each rotation
thanks for showing concern
Oh look at that I was going to tell you something about the setup, I've heard that working with ORR is quite hard because oxygen solubility but now it makes sense.
Good luck
We need to have more system information that is studying. Perhaps there is a step and product hidrolise.
No i don't think so ...these are stable oxides and am studying in 0.5M H2SO4
Well, is that when you are bubbling oxygen in the solution you need to have a very well sealed cell and you need to be careful in terms of letting the oxygen escapes, also have a pristine surface on your electrode, your reference electrode must be adequate for acid solutions if Ag/AgCl KCL satd is being used I recommend change it to RHE and stuff like that but anyways if is already working that;s good.
Best
I'm assuming you are using a frit or a salt bridge to protect the reference electrode, but remember that acid solution may change the inner solution on your reference and the potential is not the same anymore, if you are checking your reference electrode potential daily and you see if it's not changing is ok. For example Ag/AgCl KCL satd has a potential of -0.045 V vs. SCE if you check your reference against SCE you should get that value.
I recommend you to read a book call Handbook of electrochemistry , Cynthia Zoski, there is a chapter that talks about the importance of choosing a good reference for a system.
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