This brings up a point about electrochemical cells that can be really confusing! The first thing to remember is that, in any kind of electrochemical cell, oxidation (loss of electrons) always occurs at the anode, and reduction (gain of electrons) always occurs at the cathode. You can remember this using the mnemonic RED CAT & AN OX. The other thing to remember is that electrons always flow from the negative (-) electrode to the positive (+) electrode, as opposite charges attract.
- In a galvanic cell, the cathode is positive and the anode is negative. Electrons flow from the negative anode on the right toward the positive cathode on the left. This uses redox reactions to create electrical energy in the form of current.
- If this were instead converted into an electrolytic cell, energy would be supplied from a power source to power the flow of electrons in the opposite, otherwise nonspontaneous direction: from the cathode on the left back toward the anode on the right. However, the charges of the anode and cathode must be reversed, as electrons will always flow toward the more positive electrode. Thus, electrons flow from the (now NEGATIVE) cathode toward the (now POSITIVE) anode.