I use the common method in the literature to detect the concentration of hydrogen peroxide, that is, to make a standard curve with cerium sulfate solution and detect the concentration of hydrogen peroxide. Among them, when testing the i-t curve, the electrolyte is 0.1 MK2SO4, and the reference electrode is gong/mercuric sulfate. At the -0.3 V vs.RHE potential, when the current reaches about 30mA, the yield can reach about 7 mol/g/h, but the Faraday efficiency is greater than 100%. . I would like to ask what is the cause of the problem and how to solve these problems. I look forward to answering this question. Thank you very much!
Dear colleague,
I have encountered this issue in my own research as well. Some possible explanations for what you observed in your experiments include:
- If the calibration curve was prepared using a cerium sulfate solution, it may have underestimated the H₂O₂ concentration. This can occur because the commercial grade (typically 30–35%) often contains stabilizers that interfere with cerium during titration, leading to inaccurate results. This issue can be resolved by using a certified reference standard that is free from stabilizers.
- If you are using oxygen (O₂) as the reactant for H₂O₂ electroproduction, you are likely applying the two-electron transfer pathway in the Faradaic efficiency calculation, which is the standard route for H₂O₂ formation and provides the theoretical concentration. However, an alternative one-electron transfer pathway may occur, producing a hydroperoxyl intermediate (∗OOH) that desorbs from the electrode and undergoes a chemical redox reaction, also leading to H₂O₂. If this pathway is significant, the assumption of two-electron transfer in the Faradaic equation should be reconsidered. The presence of ∗OOH can be confirmed using electron paramagnetic resonance (EPR).
I hope these considerations help you in some way, and I wish you the best with your research.
Dear Dr. Souto，
I'm glad to receive your reply. Your answer shows that you are a very professional scientific researcher.
First of all, I have the following views on the first possible reason for your improvement. My standard curve is the concentration gradient of pure cerium sulfate (0.1nM 0.2nM 0.3nM 0.4nM 0.5nM), which is not the standard curve drawn by the absorbance of cerium sulfate after the reaction of commercial hydrogen peroxide.
Regarding the second reason you metioned, I would like to ask further advice. If this is really the reason,
how should I solve this problem?
Thank you very much for your letter again. I look forward to hearing from you again.
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