zephler1
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organic electrochemical questions
A few questions, can someone help?
1. When calculating current density, do you consider only one face of the cathode, or both faces (to calculate surface area). It makes sense that it
might be proper to consider both, since both are exposed to the reaction mixture. In practice however, I would assume that the vast majority of
electrons would choose the shortest path to the anode; hence only considering the face of the cathode that faces the anode is sufficient to determine
current density.
2. For an electrolytic reduction of an organic species, is material selection for the anode important? Since the "working electrode" (cathode) is
the one doing the reducing, I would assume that any material that can conduct a current and is chemically stable (as in it doesn't dissolve into the
electrolyte) would be fine to use. Is this just plain wrong?
Thank you for your help!
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morganbw
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I worked in an electro chemical process for 19 years and have a little experience in this area.
For the most it is okay to use the short path equations for the current density. This does not mean that current from the back of the cathode or anode
does not happen, it does indeed happen but unless your are a purest and just wish to have a perfect model ( it can normally be ignored )
No clue as to what you are after but in my experience the Anode choice has always been the most important. If not selected properly it will degrade.
The cathode however, well, ever hear of cathodic protection?
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zephler1
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Thank you for your reply. My interest is in Organic Electrochemical synthesis. I appreciate your comments about anode selection. Besides corrosion
and degradation, are there other considerations, such as if the incorrect anode is selected, would the overvoltage of the cathode be affected?
Explained another way, a reduction of an organic was performed in a divided cell using a lead cathode and a DSA anode. The literature method suggests
a lead cathode and a lead anode, however, the article is quite old, so I don't think that DSA's existed at that time. The DSA anode was selected for
the reason that you state, as in it will not corrode in the electrolyte. The reaction produced some strange material, and not the intended target.
Yes, the obvious answer is to use exactly what is in the literature method, but from an academic or personal interest side of things, I was wondering
how the anode could have had that much of an effect on the outcome, since the reduction is being performed at the cathode?
Since you have some experience in this field, I am also wondering if you could recommend a method for the pre-treatment of a lead cathode with PbO2?
So far, the lead cathode and a lead anode are ran for 20 minutes in 20% w/v H2SO4 for 20 minutes in there regular configuration. They are then
switched, as in the cathode is ran as an anode and the anode ran as a cathode, again for 20 minutes. The current density for each step, for the first
10 minutes is 100 mA/cm^2, and then for the final 10 minutes at 200 mA^2. Do you think this initial treatment should be ran for longer?
Thanks again for your input!
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