I am depositing Ni on the home made electrode/substrate via cyclic voltammetry. During deposition at high number of cycles some white thing(a big suspension) is releasing from the substrate. Is that the deposited Ni removed from the substrate after deposition due to I use high number of cycle(~500)? In my perception using high number of cycles I will get more Ni deposited on the substrate.
Is there a possibility of optimum number of cycles to get high amount of Ni deposited?
Please help me, thank you
Instead of cyclic voltammetry, chronoamperometry would be more effective towards electrodeposition of metal, here Ni, where the amount and quality of the film could be tuned by time and potential. In addition, cyclic voltammetry would not be a good choice for deposition as the deposited material would undergo oxidation during the anodic scan.
Well, I shall try not to be too generic about my answer but you should consider a couple of things (if you haven't already) before you do CV
1. Make sure whether you are really depositing Ni or you are plainly destroying your electrode surface due to extensive number of cycles and inappropriate CV window. This means you should choose the right electrode system and parameters.
2. If step 1 is verified, you must count the number of cycles till which the suspension is not seen. If you are depositing something definitely the current shall increase with increased number of cycles. See if your Randles-Sevick Parameters are behaving according to the equation and conditions.
3. To get the amount of Ni, one typically performs QCM (Quartz Crystal Microbalance) measurements. So try to systematically find a relation between mass adhered to electrode surface versus CV cycles.
4. If still the white substance piques your interest, collect it and try to identify what exactly it is, whether a product of electrode corrosion or some solid redox species from solvent or analyte.
Thank you.
please. tell us more abount your experimental condition, like what is in your electrolyte beside Ni salt and your potential window
Instead of cyclic voltammetry, chronoamperometry would be more effective towards electrodeposition of metal, here Ni, where the amount and quality of the film could be tuned by time and potential. In addition, cyclic voltammetry would not be a good choice for deposition as the deposited material would undergo oxidation during the anodic scan.
Alaa is right on questioning about your experimental conditions.
It is obviously inappropriate if your potential range was extended to be more positive than that for anodic dissolution of Ni. If this was the case, you would dissolve part or all of the deposited Ni during the positive potential scan.
Cyclic voltammetry has been designed for analysis, instead of production of materials. However, it may be used to deposit a material if there is a special need, such as in the case of conducting polymer deposition. For Ni deposition, cyclic voltammetry may also help avoid or slow dendrite formation.
Mulatu- I also agree with Sujoy that Cyclic Voltammetry is not the best choice for the electrodeposition of a metal, compared to chronoamperometry. Possibly the white substance you are observing is a nickel oxide or nickel hydroxide that does not adhere to your surface which you continually generate with each additional cycle. However, we would need more details about your potential window, electrolyte, etc. in order to provide more help
I just noticed a down-vote to my answer above. I therefore would be grateful if the friend down-voted my answer may let me know (either post your explanation here or email me privately) what you think/believe in my answer above was inappropriate or incorrect.
George Zheng Chen, really I would like to apologize you about the voting system, because i was not familiar regarding it. I understood today the arrows of voting system, sorry sorry again!!! I may click the down arrow by default without deliberately.
First, I would like to thank you all. To make brief the question, the CV potential range was -1.5 to -0.5 V Vs Ag/AgCl. Because in this range only reduction is expected due to reduction potential of Ni is around -0.25 v Vs RHE and evolution of H2. The electrolyte solution are NiCl2 and Na2SO4 (supporting electrolyte) with pH ~6.0. I tried with chronoamperometry, however better (more) Ni is obtained by voltammetry after analysis with CV, EDX and SEM test. I will try again via chronoamperometry ofcourse. Thank you!
George Zheng Chen, my private email is: [email protected]
Mulatu Birhanu, thank you for your explanation. No problem, and I was more interested to know if I wrote something incorrect, instead of your unintended down-vote.
According to Wikipedia, Ni(OH)2 is green in colour, and I know NiO is also green. This means the white suspension you observed was unlikely Ni(OH)2. You did mention that the white suspension was released from the "home made" substrate. So, it seems to be a mystery of your substrate, but not related with the deposited Ni. Because your potential range was sufficiently negative to invoke reduction of proton to hydrogen gas, the solution around the cathode would become alkaline. This means that if your solution or substrate contained other metal ions, such as Mg2+, white precipitate would form.
For your information, in the industry, electro-deposition of Ni is carried out in a fairly acidic and sulphate containing solution (electrolyte) under constant current.
Dear George,
Exactly! That's what I expected and wrote at first. I believe its a product of substrate corrosion
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