文档介绍：Introduction to electrochemistry - Basics of all techniques -
Electrochemistry is the study of phenomena at electrode-solution interfaces
(a) Galvanic and (b) electrolytic cells
Two quite different aspects of the field of electrochemistry
The overall chemical reaction taking place in a cell is made up of two independent half-reactions, which describe the real chemical changes at the two electrodes.
Most of the time one is interested in only one of these reactions, and the electrode at which it occurs is called the working (or indicator) electrode, coupled with an electrode that approaches an ideal nonpolarizable electrode of known potential, called the reference electrode. In experiments, the current is passed between the working electrode and an auxiliary(or counter) electrode.
Three electrodes are frequently placed in partments separated by a sintered-glass disk.
Reactions and electrodes
Three-electrode cell and notation for the different electrodes
● The potential of the working electrode is monitored relative to a separate reference electrode, positioned with its tip near the working electrode.
● The internationally accepted primary reference is the standard hydrogen electrode (SHE) or normal hydrogen electrode (NHE), which is
Pt/H2(a=1)/H+(a=1,aqueous)
●By far the mon reference is the saturated calomel electrode (SCE), which is
Hg/Hg2Cl2/KCl(sat’d in water)
Its potential is V vs. NHE.
Reference electrode
Introduction
Investigation of chemical phenomena associated with a charge transfer reaction
To assure electroneutrality two (or more) half-reactions take place in opposite directions (oxidation/reduction)
If the sum of free energy changes at both electrodes is negative electrical energy is released battery
If it is positive, external electrical energy has to be supplied to oblige electrode reactions electrolysis
Introduction
Scope of electrochemistry
In general, the electrode reaction rate is governed by rates of processes such as:
Ma