Hello everyone!

I am having some issues with my potentiostat. To troubleshoot, I decided to go back to the basics and do a simple CV of 0.1 M NaCl with two gold electrodes and an RE coated in house (Ag/AgCl in 3.5 M NaCl).

I am trying to get the same peaks found in papers with similar conditions:

• Source 1 (

  Article Anodic Oxidation of Chlorides on Platinum Modified by Metallic Oxides

  ) reports narrow duck shape with -ve peak at ca 1.2 V vs. SHE (Pt electrodes, 0.1 M NaCl)
• Source 2 (

  Article Molecular Design of Semiconducting Polymers for High-Perform...

  ) reports ca. 1.2 V abs +ve peak, (ITO glass coated with conductive polymer WE, Pt CE, 0.1 M TBAPF6 supporting, 0.1 M NaCl)

What I am expecting:

• A sharp peak for OER at ca. 1.0 V (vs. my RE)
• A broader, smaller peak for HER at ca. -0.2 V (vs. my RE)

What I consistently observe:

• My gold electrodes look corroded (CE more so than WE)
• Bubbles form at both (more at CE)

What I have tried to rule out:

• Alligator clips interfering: they are protected by heat shrinking
• Influence of scan rate: tried 5 mV/s, 50 mV/s and 100 mV/s
• Dirty/dry frits: replaced

Description of the plot:

• black curve (broad, noisy peaks at ca. -0.3 V and -0.03 V) features older/dry frits, 5 mV/s scan rate
• red curve (sharp peaks at ca. -0.3 V, -0.03 V) features fresh frits, 5 mV/s
• from there, I did not replace the medium: I used the same 0.1 M NaCl solution used to collect the red curve. As you can see, the remaining three curves (frits2, 50 mV/s; frits3, 100 mV/s and frits_rep, 5 mV/s) progressively get flatter and noisier.

I think there is some contamination or a side reaction occurring, and I can't figure out why:

• The red CV plot has sharp peaks, and not in places where I would be expecting them.
• After I stopped replacing the solvent + elyte, my graphs got noisier and flatter.

Is there any other way I can troubleshoot this? I feel like I should be able to replicate such a simple experiment, but I am obviously missing something.

Other possibilities:

• I found papers about gold reacting with chlorides and now I am wondering if that is an issue - however, that usually occurs at higher positive potentials above 1 V vs. SHE.
• I am thinking about whether my Ag/AgCl might need to be recoated. This seems plausible.

I am also thinking about whether both might be true:

• There is ca. a 0.3 V difference between my peaks. If my Ag/AgCl needs to be recoated, and the electrode potential shifted down significantly, that would support me observing OER (negative peak, usually 1.2 V vs. SHE) and formation of some Au-Cl ion (1.5 V vs. SHE, various sources).
• This goes against my understanding that gold is quite inert as an electrode - now that I am doing a Google Search, I am finding that cyanide and chloride-containing electrodes are not compatible with gold electrodes.
• If this was the case, the gold chloride anions would be accumulating over time, saturating the surface of the gold (which appears as corrosion) and slowing the reaction as there is not much reactant left.

Anything else to disprove my thoughts? I am new to electrochemistry and would love more opinions and experiences. Thank you kindly for reading all of this,

Michela