How one should start then to find the potential window of electrolyte and various working electrodes (Au, Pt, GC, Ag). Isn't there any database available on this ?
Answer of your first question is to carry out experiment with a specific electrode and the electrolytic medium. Mentioning that it is a must to use reactive gases (especially O2) free electrolytic medium, i.e., before doing experiment one must bubble the medium with inert gases, e.g., N2, He, Ar, you may know. In case of ionic liquid medium, other gases especially CO2 also shows its reactive behavior. However, generally we must make an inert electrolytic environment for knowing the electrochemical potential window.
Electrochemical potential window, off course, varies electrode-to-electrode even using the same medium. So potential window depends on the set of electrode and electrolytic medium and is a measurable quantity.
The answer of second question is not straightforward. You may find some data of potential window for commonly used electrode and electrolytic medium in books. For ionic liquids you may find in recently published journals, but content of impurities especially water in ionic liquids provide misleading potential window.
Thank you Dr. Islam. Could I have more light onto it. I am not willing in ionic liquiids and want to know possible potential in aqueous electrolytes (PB, 0.1 M HNO3, 0.1 M H2So4, HcLo4, )