Hi all, I have some history in practical electrochemistry, and have, I think, a reasonable uderstanding of the basics of Redox reactions and ½ cells. Recently, I have been thinking about a project, and it has me in a complete quandry. There’s probably something obvious that I’m missing, but here goes. To set the scene, take the classic galvanic cell situation in which we have 2 separate compartments. One contains Zn with a molar electrolyte, and the other Cu with same. The Zn will be oxidised, and the Cu reduced with the appropriate potential. We use a salt bridge to connect the 2 compartments in order to combat the build up of Zn ions in one cell, and the depletion of Cu in the other. Now imagine an electrolytic cell pair which both contain Cu, and a molar electrolyte. Now, we have an external power supply which supplies the necessary p.d. to cause the reduction of Cu in one cell, and the corresponding oxidation in the other. If we link the 2 with a salt bridge, this should keep going for quite a while- it is a valid and stable situation. The power supply ‘expects’ to see electrons leaving the negative pole, and this does indeed happen. They are consumed in reducing the Cu ions. Also, electrons are arriving at the positive pole due to being donated by the oxidising Cu at the anode. This doesn’t need to be a theoretical type cell in which we are looking for full reversibility, and therefore and almost zero current flow, as we can afford to push a bit to get some volume transacting. The requirements are being met. The current flow is being fully maintained by the redox reactions, and is provided by nF electrons flowing, directly connected to the Cu redox rate. Instead of a salt bridge, we can use a small pump to circulate the electrolyte to even out the concentrations, because the 2 solutions don’t need to be separated for chemical reasons. The reason for the separation is an operational one. Comparing this to a commercial copper electrolyser, how is it that I can’t get out of my head that current density is all about electrode spacing, and that the above won’t happen. I can’t find a problem with running this reaction in the above way. Your arguments would be greatly appreciated.