The Continuous Flow of Electrons across an Interface Electrochemical Reactions

The Continuous Flow of Electrons across an Interface Electrochemical Reactions 

It has been argued in the preceding section that all surfaces carry an excess electric charge, i.e., that surfaces in contact with ionic solutions are electrified. However, the argument was made by considering an isolated piece of material unconnected to a source or sink of electrons. 

Suppose now that the metal, an electronic conductor, is connected to a power supply, i.e., to a source of electrons so large in capacity that, say, lo to 10 electrons drawn from the source leave it unaffected in any significant way. To make the discussion specific, assume that the electronic conductor is a platinum plate and the ionically conducting phase is an aqueous solution of HI. 

What is being described ha-e is an electrochemical reaction i.e., it is a chemical transformation involving the transfer of electrons across an interface, and it can be written in familiar style as 

The hydrogen ions are discharged (neutralized) on the electrode and there is an evolution of hydrogen outside the solution, as a gas. 

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