So, I am doing electrodeposition of Zn onto carbon fabric, which is my working electrode. As reference electrode, I used Ag7AgCl in 3M KCl, and as counter electrode, I used a Zn plate. After varying the current density, I see that the cathodic potential increases. Is it something to do with Gibbs energy? or the ease of overcoming the barrier to form Zn onto the cathode?
Yog Ram The observed increase in cathodic potential during your Zn electrodeposition onto carbon fabric could be attributed to a combination of factors, including overpotential, kinetic, and the ease of overcoming the barrierfor Zn reduction at the cathode.
- Wu, M., Zhang, G., Yang, H., Liu, X., Dubois, M., Gauthier, M. A., & Sun, S. (2022). Aqueous Zn‐based rechargeable batteries: recent progress and future perspectives. InfoMat, 4(5), e12265.
- Zhou, M., Chen, Y., Fang, G., & Liang, S. (2022). Electrolyte/electrode interfacial electrochemical behaviors and optimization strategies in aqueous zinc-ion batteries. Energy Storage Materials, 45, 618-646.
I hope these articles are helpful for you.
Best regards,
Alvena Shahid
You're on the right track! The observation that the cathodic potential (potential required for zinc deposition) increases with increasing current density is likely related to both factors: activation energy and Gibbs free energy.
Here's a breakdown:
- Activation Energy: Electrodeposition of Zn onto the carbon fabric involves overcoming an energy barrier for the reaction to proceed. This energy barrier is known as activation energy. Higher current densities essentially mean you're trying to force the reaction to happen faster. This increased rate requires more energy to push the reaction over the activation energy barrier, leading to a more negative (more cathodic) potential.
- Gibbs Free Energy: While activation energy represents the initial hurdle, the overall favorability of the reaction is determined by Gibbs free energy. A negative Gibbs free energy indicates a spontaneous reaction (Zn deposition in this case). However, the polarization effects caused by high current densities can effectively make the reaction appear less favorable. This can be visualized as a shift in the electrode potential required to maintain the necessary reaction rate.
In simpler terms, increasing current density demands a more negative potential (more cathodic) to both overcome the initial energy barrier (activation energy) and counteract the polarization effects that hinder the reaction at high rates.
So, it's a combination of both factors influencing the observed increase in cathodic potential with higher current densities.
Monika Antil Alvena Shahid Thank you very much.
Monika Antil, I thought that for this case of Zn deposition onto carbon fabric using the 3-electrode setup, it would result in a positive Gibbs energy.
G=-nFE, and E is calculated by E=E0-EAg/agCl = -0.76 V- 0.2 V. Or is it wrong?
Your calculation of the combined electrode potential (E = E⁰_Zn -E⁰_Ag/AgCl) is correct
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction