What kind of RE are you using? Unless your RE is leaking (i.e. the frit is imperfectly sealed), the difference in concentration should not be a problem.

If possible, please post a picture of your CV - the nature of the noise can give many clues as to the "culprit" behind it.

A few things you might ewant to check:

1) Is your cell subject to any kind of mechanical vibrations / interference? Sometimes, a loosely hanging electrode can cause significant noise due to micro-stirring of your experimental solution

2) What are the current range settings on your potentiostat? If the potentiostat is set to automatic current range determination, it might help to set it to a particular current range (choose the range based on your "noisy" CV).

3) Is the temperature of your experimental solution noticeably different from the temperature of the room? Changes in solution temperature result in movement of the hotter/colder solvent in the cell and cause all kinds of havoc.

What is your procedure for preparing the electrodes for the measurement? I'm not an expert on AOR, but polishing electrodes without sufficient removal of the polishing agent is also a common "culprit".

Tomasz Jarosz

Hi Tomasz,

Thanks for your response.

I am using Ag/AgCl as RE. No leakage as I have checked a couple of times and I have about 3 of these REs at my disposal, so I can interchange and check if there is any leakage (issues) with either of them.

See below the picture of one of such noise.

To your questions;

1. No mechanical vibration / interference as the lab is set up in the basement of the building and the experimental setup is on a standardized experimental bench. In addition, am not working on a hanging electrode.

2. From the picture, I have worked between -0.7eV and 0.6eV. However, I do work also in the range of 0eV and 1.4eV

3. The experimental solution has been prepared hours prior to the the measurement, and given enough time to acclimatize to the room temperature. As regard to the GC electrodes, I follow the standard rules. Polishing via the "8" pattern using 0.05um polishing alumina once in 5 days on the polish and DIW for rinsing.

Do you have any other suggestion?

Thanks once again

Thank you for the CV picture. This noise seems to present only in the anodic half-cycles and only after (at potentials above those of) the oxidation peak at approx -0.24V. Did you observe it in other parts of the CV in other experiments?

The nature of the noise is what I would expect of a disturbance in the electrical double layer. Had you not mentioned that no bubbles evolve during the measurement, I would suspect their interference. Does that also apply to the RE and CE? Is there any visible change to the surface of the WE?

Ad. 3 While I do not expect it to be an issue, since you have observed this noise on different WEs, I would recommend placing the WEs in DIW in an ultrasonic bath (5-10mins has always been enough in our case) to dislodge any micro-scale fragments of alumina that may be attached to the WE surface.

Did repeating the scan at lower scan rates (as you originally mentioned) help anything?

Tomasz Jarosz

Hi Tomasz,

For other experiment such as MOR and EOR, while using same catalyst, I do observe noise at the cathode as well.

Yes there are presence of gas bubbles at the surface of the WE in some of the measurement example is MOR.

I have cleaned the WEs using DIW in an ultrasonic bath, however, i still get those noise both at the anode and cathode while doing measurement for EOR.

If there are gas bubbles and you see the noise regardless of potential applied at the moment the noise occurrs, then the gas bubble is the culprit.

That said, getting rid of thatculprit may prove tricky -most means of dislodging such a bubble would also cause the electrode to be disturbed and result in (possibly even larger than what you see) noise.

Frankly, for publication, I would recommend noting on the source of the noise and leaving the CV as i, unless you can find a way of constantly removing the forming bubbles.