More specifically, the system I am using involves sputtered/ebeam evaporated platinum microelectrodes ~50*50 micrometers spaced apart at roughly 50 microns too. A current current pulse of 1-4 uA for 2-5 seconds is injected. I am confused about the presence of additional salts in PBS affecting the evolved gas. From basic Nernst equation relationships I believe it's possible to compute hydrogen and oxygen evolved from H20 given the standard potentials but are there other interesting charge transfer resistances introduced by additional ions? For instance, how might one begin to model chlorine gas evolution from the chlorine ions. The next step would also be to try to understand dissolution of the small microbubble that was just generated as well since Pt is a well known catalyst for H2 and O2 recombination.
Thank you for your time and please let me know if there is anything I can do to clarify.
Hello Eugene,
First can you confirm details on your PBS composition. For instance, I have seen some include Mg and Ca ions.
Kind regards,
Jules
Absolutely, thanks Jules.
1X Solution Composition is 137 mM NaCl, 2.7 mM KCl, 9.5 mM Phosphate buffer (Disodium orthophosphate heptahydrate).Does not contain magnesium or calcium
Having a reference electrode would really help, since that way you'll see what potential your Pt electrodes experience when you run a current, and that should point you to the right reactions. On the negative, you're probably making H2, since that seems the only thing to evolve on reduction. On positive, it's probably Cl2. Oxygen evolution is possible, but the overpotential for that is high, 0.77V on Pt, which means that you'll need 0.77+0.82=1.59V to make it at pH=7. Meanwhile chlorine overpotential on Pt is low, 0.08V, so you'll be evolving Cl2 at 1.36+0.08=1.44V, much more readily.
Nernst equation will tell you about whether thermodynamics of the reaction are favorable, but it tells you nothing about kinetics, which is where your overpotential comes in. I hope this helps.
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