Hello all :) i am researching non-PGM electrodes for HER and OER reactions in pH14, for water splitting application. Curiously, i found that the moment PGM materials are replaced for HER, the overpotential contribution is relatively higher compared to non-PGM OER I am using NiFeCo-NickelFibre as HER and NiFe2O4-SS316LFibre as OER. Any thoughts?
No thoughts. The thermodynamic of water splitting is described in text-books. The standard delta G of the 2H2O - O2 + 2H2 overall reaction is 1.24 v and pH independent. For potential required to proceed the half-reaction 2 H+ + 2e- -> H2 is 0.06*pH. For water oxidation 1.24 - 0.06*pH. Your data must be consistent with those values
Hi Yuri, Thanks for your response. Indeed the reversible potentials follow the Pourbaix diagram, as a function of pH.
However, my question is related to relative overpotential (Kinetics) contribution between OER and HER. Most of the literature I find, nearly take it for granted, that the OER overpotential is higher than the HER as a function of current density. I am questioning the basis of this observation and would like to identify if there could be an exception.
The value of calculated overpotential depends on the reaction mechanism. . In general, water oxidation is considered as 4-electron process, while water reduction is 2-electron. Water oxidation may proceed through the hydrogen peroxide intermediate formation. The overpotential for the second pathway is different. To continue the discussion, please, describe how do you calculate the "relative overpotential (Kinetics)?"
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