For the reaction at the anode:Al ----gt; Al3+ + 3eHowever, at the anode, oxygen are also produced and forms aluminium oxide(Al2O3) with aluminium.Are Oxygen produced by oxidation of water by electrolysis? or some reaction else?If Oxygen are produced by oxidation of water, then why it can be oxidise sinceAl ----gt; Al3+ + 3e E^0= + 1.66V2H2O ---gt; O2 + 4H+ + 4e E^0= - 1.23V(if refers to E null value) Oxygen should only be produced after all the Al have been finish oxidised.Both reaction happen at the same time? Is it possible?
with respect to your massege, i must say that it depends of what electrode you choice for your work. but with refer to E i think oxidation of watter do not interference with oxidation of Al and only oxidation of Al happen .
When Al is formed on the anode, it is immediately oxidized to Al2O3 because Al is very active. The oxygen come from the water. Actually, when you expose Al to the air, a layer of Al2O3 is formed and passivates the surface, this means, the surface do not continue oxidizing.
Anodising is a process in which the surface of a metal is modified. In the case of anodising aluminum the layer of aluminum oxide is made thicker. This is done by placing the aluminum in a sulfuric acid solution and passing a current through it so that it serves as an anode-the current releases oxygen at the surface of the aluminum increasing the aluminum oxide. I'm pretty sure this is from the reaction of the electric charge and the sulfuric acid producing oxygen as you showed in your last reaction with water. I hope this was helpful, I'm at work and don't have my old chem books and I dont' remember all this stuff off the top of my head.
