Present some more details, please, about your cell, dear Zora Hirbodvash.

Also, what is the potential window ?

Thank you so much. I appreciate your time and help.

The system consists of three electrodes, Au working electrode, Pt wire as the counter electrode, and Ag/AgCl reference electrode. The measurements( current Vs. potential) were carried out using 70 ml of 1 mM potassium ferricyanide dissolved in 100 mM potassium nitrate as the supporting electrolyte in different scan rates. Sometime, during cyclic voltammetry, I could see some bubbles form at the surface of the working electrode. These bubbles formation do not happen always and don't form at the same time (for example, it happens at the beginning of the experiment in some cases, and in others, it happens after a few minutes).

The potential window is excitation front or applying voltage (triangle form) we applied on the working electrode relative to the reference electrode.

Thanks again

Dear Zora Hirbodvash

Are you using RDE (rotating disk electrode) Au electrode of just Au foil as working electrode?

Are you doing the test in Argon/nitrogen saturated electrolyte?

As mention by Dr. Ioannis Samaras , tell us about the potential range?

Thank you!

Bapi

Is your supporting electrolyte oxygenated or de-oxygenated? In both cases those bubbles could produce a noisy voltammogram. You can get rid of them by purging a bit of the gas that you use for your experiments.

In addition to electrolyte's contamination[1] (noted above: Bapi Bera, Firas A. Al-Lolage), the low purity of the WE (Au-foil) might be the source of triggering bubbles[2] at sites of impurity (micro-)clusters,

a) in the middle of the (nominal for Au) potential range, and

b) at low(er) scan rates.

So, what is the purity[3] of your Au (WE) ?

1. Cyclic Voltammetry noise is proportional to the scan rate. Zora Hirbodvash could you show some CVs ?

2. A partial quotation of Zora Hirbodvash: "These bubbles formation do not happen always and don't form at the same time (for example, it happens at the beginning of the experiment in some cases, and in others, it happens after a few minutes)."

3. In your case, it is recommended a high purity, (near to) 4N purity; it means a 99.99% gold purity.

Please see this paper if suitable for more information on gas bubble removal https://www.nature.com/articles/srep38780.pdf

Dear Dr. Amitava Roy ,

this[1] paper is, surely, not recommended as suitable for gas bubble removal, at least, in case of the Au, and all other NON-porous electrodes.

1. How to Enhance Gas Removal from Porous Electrodes ? https://www.nature.com/articles/srep38780.pdf

It is not clear what is this electrode for in the question above. I have handled the formation of gas bubbles as a desired thing for example in an electrolyser producing hydrogen and oxygen from water. This will happen in a tiny lab scale experiment or large industrial size electrolysers. The fast removal of the bubbles from the electrode surface is one of the keys to improve the efficiency of electrolysers, and therefore the understanding the factors of how bubble formation takes place (e.g. surface structure of electrodes, coating on electrodes, operating pressure, depth of electrodes, orientation of electrodes, buoyancy force, flow rate etc) and at what bubble diameter it leaves the electrodes overcoming the surface tension etc) can be helpful in designing a good cell/stack.

@ Bapi Bera

Dear Bapi Bera,

Thank you for your message. No, we do not use RDE, and we are not doing the test in argon, nitrogen saturated electrolyte. By the potential window, I mean the voltage range we are applying to the system ( the interval between the end point and start point of voltage we set in the experiment ).

@Firas A. Al-Lolage

Dear Firas A.Al-Lolage,

Thanks for taking the time and replying to my question. I did not do the purging for my experiments.

@Amitava Roy and @ Ioannis Samaras

Dear Amitava Roy and Ioannis Samaras,

Thank you for sharing the papers and discussions. I will have a look at them.

@ Ioannis Samaras

Dear Ioannis Samaras,

I am grateful for your taking the time and replying to my question. I do not know the purity of the gold working electrode. I tried to find this information on the package from the company, but I could not find anything. Please find a set of CV in different scan rates attached.

Dear Zora Hirbodvash , a part of the 'noise' in your low rate (= < 2mV/s, in RGE.png) CVs might be attributed to corrosion and the following (usually invisible) micro-bubbles, at impurity (micro-)clusters sites of your (low purity) WE (Au), as a 'multi-WE', e.g. a Au-based-WE.

Ioannis Samaras Thank you so much for your time and help. I will check the purity of the gold working electrode with the company. I have the same problem( formation of bubbles) in the chip (die) structure I have. I am doing the same experiment I explained. The die is made of straight Au waveguide (used as a working electrode) next to the Pt strip (used as a counter electrode). I use Ag/AgCl reference electrode, and the electrolyte is made of 70 ml of 1 mM potassium ferricyanide dissolved in 100 mM potassium nitrate as the supporting electrolyte. I do the cyclic voltammetry in different scan rates and I am quite sure about the purity of gold, but still those bubbles form sometimes. Do you have any idea about it?

Thanks again,

Zohreh

Dear Balaji Dhopte

a temporal removal of bubbles is, let me say, a kind of a 'minor' issue.

The main issue of some 'steady state', or reappearing, at impurity (micro-)clusters sites, new, bubbles is/are the WE (Au-) impurities.

Balaji Dhopte

Thank you both for your insights.

About my experiences:

Bubbles are a gas. A gas is dissolving in a solution depending on the temperature of the solution. The cooler the solution the better it is dissolving.

If you cool down a solution ("pre-heated") within your measuring chamber, the gas is getting dissolved in comparison to the warmer condition. The bubbles disappear immediately.

Monika Bozem

Thank you very much. I will try that.

In present window no bubbles should be form. What is starting and switching potential of this experiment? What is supporting electrolyte used?

Abdulaziz Amro

Thank you for taking time, and replying my message. The starting potential is 0 V, and switching potential is 0.5 V. The measurements were carried out using 70 ml of 1 mM potassium ferricyanide dissolved in 100 mM potassium nitrate as the supporting electrolyte.