According to composite state of electrode material, electrode could be divided into three types. The first type of electrode is metal electrode and gas electrode, such as zinc electrode and copper electrode of Danial battery and standard hydrogen electrode. The second type is metal-metal insolube salt electrode and metal-metal refractory oixde electrode, such as Ag-Ag CI electrode. The third type is redox electrode. (Any electrode is redox electrode. Here what we mentioned redox electrode specially refers to material joined to electrode reaction are all in the same solution). Such as the electrode composed by Fe3+ and Fe2 liquor. Electrode is the conductor when current comes in or leaves electrolytic liquor during electrolytic process. Electrolytic process is the oxidation reduction reaction in the electrode interface.
Electrode is divided into cathode and anode. The side connecting with positive power supply is anode, which takes place oxidizing reaction while the side with negative power supply is cathode and it takes place reduction on the cathode. There are many kinds of electrolytic material. The most often used is carbon electrode. Besides, titanium and other metal can also be used as electrode. During electroplating, metal which coated metal is normally used as anode and the products to be plated is used as cathode.