I am using Ag/AgCl electrode for alkaline seawater splitting. As 1M KOH is not suitable for Ag/AgCl nbecause high alkaline condition electrode potential is Ag2O. I am using 0.5M KOH. For extra care we rinsed the electrode with 3M KCl solution before each measurement. We have Hg/HgO electrode but I found that Hg is sensitive to chloride anion. We know that salt concentration is high for sea water condition. Will it be accurate or minimum error in electrode potential in this condition (seawater+0.5M KOH)?
This is a fascinating application. Let's delve into the option:
1. Ag/AgCl Electrode:
○ The Ag/AgCl electrode is widely used as a reference electrode in electrochemical measurements.
○ It provides a stable and reproducible reference potential.
○ The Ag/AgCl system maintains a constant potential due to the reversible Cl^-/AgCl redox couple.
2. Seawater Splitting:
○ Seawater splitting for hydrogen evolution is a promising clean hydrogen energy harvesting technique.
○ The goal is to generate hydrogen gas (H₂) from seawater through electrolysis.
3. Electrolyte Choice:
○ You mentioned using 0.5M KOH instead of 1M KOH.
○ This is a good choice because high alkaline conditions can lead to the formation of Ag₂O on the Ag/AgCl electrode, affecting its potential.
○ Lowering the KOH concentration helps mitigate this issue.
4. Rinsing with 3M KCl Solution:
○ Rinsing the electrode with 3M KCl solution before each measurement is prudent.
○ KCl helps maintain the stability of the Ag/AgCl electrode by replenishing the Cl^- ions.
5. Hg/HgO Electrode Sensitivity:
○ You mentioned having a Hg/HgO electrode.
○ Hg is indeed sensitive to chloride anions.
○ In seawater conditions, where chloride concentration is high, this sensitivity could introduce errors in electrode potential measurements.
6. Accuracy and Error:
○ The accuracy of electrode potential measurements depends on several factors:
■ Ionic strength: Seawater has a high ionic strength due to dissolved salts. This affects the double-layer capacitance and can impact the electrode potential.
■ Chloride concentration: The presence of chloride ions affects the Ag/AgCl electrode potential.
■ KOH concentration: Lowering the KOH concentration helps minimize Ag₂O formation.
○ While the Ag/AgCl electrode is commonly used in seawater studies, it's essential to consider these factors and calibrate accordingly.
Using the Ag/AgCl electrode in seawater with 0.5M KOH and proper rinsing procedures should yield reasonably accurate results. However, be mindful of the Hg/HgO electrode's sensitivity to chloride ions. Regular calibration and validation against known standards are crucial for minimizing errors in electrode potential measurements.
Source(s)
1. Seawater splitting for hydrogen evolution by robust electrocatalysts ...
2. Investigations into electrochemical water splitting - Enlighten Theses
3. Impedance characteristics for solid Ag/AgCl electrode used ... - Springer
4. Insights on the Electrocatalytic Seawater Splitting at Heterogeneous ...
5. https://doi.org/10.3390/molecules26195926
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