For example take cobalt oxide one can find literature's reporting 0 to 0.4 V, 0 to 0.45 V, 0 to 0.5 V, 0 to 0.6 V etc. (similar reference electrodes used) potential window in aqueous KOH electrolyte. Why same materials exhibits different potential window in same electrolyte ?. On which material property (like crystallinity, surface area, porosity etc.) does the potential window of the material depends ?
I have come to find that defining potential window at an electrode could be arbitrary. When CV is used to estimate this window, various researchers use different current density cut-offs to define the window. Besides, the synthesis and fabrication methods of the electrodes may introduce a few property variations.
@Isaiah. Sir, is there any specific property of the material the potential window can be directly related
in aqueous solution the potential window is decided by pH and electrode
in other words Fermi levels for electron transfers for oxygen and hydrogen reactions in water and Ef for the electrode materials
The reactions at the potential window are Faradaic and as such, will be affected by the electron exchange ability of the electrode. The electronic structure; density of states, Fermi level, band gap (if any) is very important in the kinetics of the reactions. For some electrodes (especially carbon materials), heterogeneous morphology (e.g combination of edge and basal planes) can have huge impacts on the reaction kinetics. In this case, the edge plane introduces reactive sites for fast electron transfer.
hello Isaiah
can you correlate Fermi level with surface morphology?
we discussing thermodyanamics
rates are not thermodynamic-- they are kinetcs
Prof. Muralidharan,
I was rather correlating electronic structure with kinetics "The electronic structure; density of states, Fermi level, band gap (if any) is very important in the kinetics of the reactions" The fact that there is a reduced overpotential may be an indication of improved kinetics for the same reaction. For carbon materials, edge planes have higher DOS than basal planes
Prof. Muralidharan,
You have mentioned, in aqueous solution the potential is decided by the pH. In that case using different mole concentrations of same electrolyte should change the potential window. I have tried CV using 1 M KOH and 3 M KOH the results remains the same.
activity of water changes with KOH concentration
we use 6MKOH+1MLioH for batteries due to this and carbonation
dear Artur
the part of the electrolyte is to determine oxygen and hydrogen evolution potentials
certainly the polar, non polarity and mixed solvents play a role
for example we use DMSO in plating to postpone H2 evolution
regarding DOS and Fermi levels
Only Fermi levels decide
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