Thought Experiment I Curve A

At first, no current flows through the cell until a decomposition potential Ed- is reached. At that point, the current begins to flow (Curve A). We also observe that gas bubbles are formed at the working electrode, and that current fluctuates somewhat randomly. Two chemical processes are taking place at the electrodes. At the W electrode (which is now the cathode), electrons are transferred from the electrode to the hydrogen ions, H+. Thus, the reduction takes place at the cathode, according to the following electrochemical reaction. 

Because the electrical circuit is closed, the opposite (oxidation) electrochemical reaction takes place at the larger AUX electrode, where the electrons leave the solution. So, at the anode, we have 

for the transfer of two electrons through this electrochemical circuit, one molecule of water is decomposed (electrolyzed) to half a mole of oxygen (at the anode) and one mole of hydrogen (at the cathode). 

This simple experiment contains a wealth of electrochemical information which we now summarize in three interim conclusions. 

Random fluctuations of the current correlate with the evolution of the bubbles at the working electrode (see FFT). 

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