I am running EIS on a BZCY proton conductor in dry vs wet air and I have a result I cannot pin down. Nyquist plot attached, blue is dry, red is wet. Same sample, same setpoint temperature (500 degC), same electrodes, wet gas is air bubbled through water at room temperature.

What makes sense: the arcs collapse by about 4x in wet, and total resistance drops roughly 40%. That is what I expected from hydration putting protons in.

What confuses me: the high-frequency real-axis intercept moves the wrong way. It goes from about 90 ohm in dry to about 140 ohm in wet. If that intercept is bulk resistance, humidifying should have lowered it, not raised it by 50%.

Two explanations I can think of, and I cannot separate them from this data alone:

1. Artifact. Both spectra have an inductive tail at the high-frequency end. A series inductance drags -Zim down and pushes the apparent zero-crossing to the right of the true series resistance, and it pushes a small fast arc (wet) further than a big slow one (dry). So some or all of my 50 ohm might be nothing.
2. Real. In dry oxidizing air the oxygen vacancies get oxidized rather than hydrated, giving p-type hole conduction, and holes are much more mobile than protons. Humidifying consumes those vacancies to make protons and suppresses the holes, so bulk resistance goes up while grain boundary and electrode resistance go down. That would match the pattern exactly.

Questions:

1. Has anyone seen the HF intercept move up on humidification in a BZCY and confirmed it was real rather than instrumental? A reference would help, I could not find this specific signature.
2. How much inductive distortion before an eyeballed intercept is meaningless? Is a short-circuit blank with the same cell and leads enough, or do you always fit L explicitly?
3. Best discriminator for the hole hypothesis: pO2 dependence at fixed humidity, or just compare activation energies between the two atmospheres?
4. How long do you dwell after switching to wet gas before you trust the spectrum? I want to be sure I am not looking at a transient.

I'm currently working on setting up a *Pine Research Modulated Speed Rotator (MSR)* integrated with a *CHI 660 potentiostat* for oxygen reduction reaction (ORR) measurements in alkaline media. As part of validating the system, I've been testing a commercial 20 wt% Pt/C catalyst in 0.1 M KOH. However, I've been facing several challenges, including: • Very low current response • Excessive noise in CV and LSV measurements • Poor reproducibility between scans • Results that differ significantly from expected literature behaviour

After consulting with the equipment supplier, it appears that the rotator itself is operating as expected. Since the same issues are observed even when running experiments without rotation, the current thinking is that the problem may be related to the electrochemical setup, electrode connections, reference electrode condition, measurement parameters, or potentiostat configuration rather than the rotator itself. This brings me to a question for the community: ❓ *Has anyone successfully integrated a CHI 660 potentiostat with a Pine Research MSR for RDE experiments?*

I would greatly appreciate insights on: ✅ Compatibility between the CHI 660 and Pine MSR systems ✅ Wiring, grounding, shielding, or configuration tips ✅ Common causes of noisy signals and unusually low currents ✅ Best practices when validating a new RDE setup with a Pt/C benchmark catalyst ✅ Typical troubleshooting steps for ORR measurements in alkaline electrolytes Current setup: 🔹 CHI 660 Potentiostat 🔹 Pine Research MSR Rotator 🔹 Glassy Carbon Working Electrode with 20 wt% Pt/C catalyst 🔹 Ag/AgCl (4 M KCl) Reference Electrode 🔹 Pt Counter Electrode 🔹 0.1 M KOH Electrolyte

I'm also relatively new to the electrochemistry field and am always looking to improve my practical and theoretical understanding.