I used Graphene oxide and Ag Nanowire modified FTO electrode for nitrate detection. But with increasing nitrate concentration , reduction peak current in CV shifts from positive to negative potential. why?
As your concentration increases, there is a greater amount of species available for reduction at the surface of the electrode. Therefore the reduction reaction is sustained longer as you continue to scan the potential from positive to negative. Remember the potential is with respect to a reference electrode, and positive/negative connotation here simply means more negative--cathodic--reduction at the working electrode or cathode. Similar to Nernst potential (and equation which is at equilibrium), the CV peaks will tend to shift to more negative potentials in a reduction reaction in a cyclic voltammogram. Since tou have not mentioned rpm or agitation, I am assuming that is held constant for all the runs.
Thank you Chandan Das. But I had a question. I got reduction peak current at around -0.1V. NO3- should show reduction peak at +0.835V (standard reductuin potential ) according to following reaction that I am expecting in my case:
NO3 - + 2H+ + 2e- → NO2 - + H2O; Eo= +0.835V
is not it? please let me know.
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