Aqueous electrolyte have a potential window of 1.2V, while organic and ionic electrolytes have higher potential windows. But what parameter is contributing to this enhancement in the respective potential window of organic and ionic electrolyte. What are the intrinsic parameters which determine the potential window of an electrolyte? Could anyone help me with an answer.
Let me first tell you that what is the intrinsic parameter due to which aqueous electrolyte have low potential window. When we talk about the electrolyte potential window, largely, it is the solvent stability which determine the potential window. the water decomposition is the major cause of getting low potential window in aqueous electrolyte. The 1.2 V is the voltage stability of pure water with respect to platinum working electrode and SHE as the reference electrode, as on the platinum surface the kinetics of water decomposition is very fast, it get reduce to evolve hydrogen at very near to 0 V and oxidise at about 1.23 V so overall potential window is 1.23 V. Further, I would like to add that when electrolyte salt has been added to the water depending on the type of electrolyte pH, the potential window can be altered.
In the organic electrolytes, the solvents whcih are generally used such as acetonitrile, ethylene carbonate have relatively higher stability upto high potential that is why the organic electrolyte can work for high potential window. Pure Ionic liquids donot contain any solvent they are the molten salts. that is why they can even be stable upto higher potential than organic electrolytes.
So the overall conclusion for your question is that the potential window stability is largely depend on the solvent stability when we consider the electrolyte stability.
Further, depending upon the working electrode material, one can obtain different working potential window.
The question is to some extant confusing. The potential window of a solution depends on windows of both electrolyte and solvent. An electrolyte might be electrochemically active and narrower than that of a solvent.
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