The redox potential of HER in pH 14 alkaline electrolyte is - 0.826 V (vs. RHE). However, for all the polarization curve I saw in articles, the authors reported the potential from 0 V (vs. RHE) toward more negative value rather than from -0.826V (vs. RHE) toward more negative.
Is it a convention to report the potential of HER in alkaline condition as their overpotential rather than the actual RHE, i.e., - 0.826 V (vs. RHE)?
Dear Shu Yu,
"The redox potential of HER in pH 14 alkaline electrolyte is - 0.826 V (vs. RHE)" This is not correct, if your samples shows HER potential at -0.826 V vs RHE value, then your sample is not good for HER. Because potential correction respect to RHE at pH 14 will be around 0.960 V. Then your samples shows HER at -1.8 V (vs Ag/AgCl).
If you take 20% Pt/C as a HER catalyst in pH 14 , the HER will start at around -1.05 V vs Ag/AgCl and if convert it into RHE the potential will come around -0.06 V (vs RHE).
Best Regards,
Bapi
Hi Bapi,
Thank you for your reply.
Could you explain to me why the below calculation is wrong for HER in alkaline environment? I followed the calculation from Nernst Equation which also complies with the Pourbaix diagram of water.
E(RHE) = 0 - pH * 0.059V
E(RHE) = -0.826V.
Maybe now it's late, moreover I'm not a genius with electrochemistry… as far as I know, HER potential is -0,826 V at pH 14 vs SHE (standard HE), not RHE (Reversible HE). So, as
E(RHE)= E(SHE)+0,059*pH
it turns that HER vs RHE at pH 14 is 0...and it keeps 0 at whatever pH. Indeed, RHE is a moving potential electrode it is defined as:
https://en.wikipedia.org/wiki/Reversible_hydrogen_electrode
Hope it's correct and it helps!
Giacomo is completely correct. It's just the SHE vs. RHE conversion.
Hi, Bapi Bera .
Could you give me, the name or DOI of the Nature paper that you mention, please?
Thanks
@ Giacomo Armani Calligaris If I want to convert SHE into RHE then how can I?
Hi Kamal, well, I guess you already know your working pH, so
E(RHE)= E(SHE)+0,059*pH
as before.
We should always look for the definitions, this helps a lot in finding our ways.
Check what's the definition for SHE and what's the one for RHE and compare them to find the differences! This will help a lot to understand better the equation and avoid misleadings!
Where does 0,059 comes from? Again, "Keep calm & check biblio" (Nernst).
In my opinion, Pourbaix diagram (sa shown by Shu Hearn Yu ) is also helpful to undersand the system if you use it with your data, but I prefer turning it with potential in x axis and pH in y axis.
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