Electrolytic vs Galvanic Cells
Electrolytic and galvanic cells are two types of electrochemical cells. In both electrolytic and galvanic cells, oxidation-reduction reactions are taking place. In a cell, there are two electrodes called an anode and a cathode. Oxidation reaction takes place on the anode, and the reduction reaction takes place on the cathode. Electrodes are immersed in separate electrolyte solutions. Normally, these solutions are ionic solutions related to the type of electrode. For example, copper electrodes are immersed in copper sulfate solutions and silver electrodes are immersed in silver chloride solution. These solutions are different; hence, they have to be separated. The most common way to separate them is a salt bridge.
What is an Electrolytic Cell?
This is a cell which uses an electrical current to break chemical compounds, or in other words, to do an electrolysis. So electrolytic cells need an external source of electrical energy for operation. For example, if we take copper and silver to be the two electrodes in the cell, silver is connected to the positive terminal of an external energy source (a battery). Copper is connected to the negative terminal. Since the negative terminal is electron rich, electrons flow from the terminal to the copper electrode. So copper is reduced. At the silver electrode, an oxidation reaction takes place, and the released electrons are given to the electron deficient positive terminal of the battery. Following is the overall reaction taking place in an electrolytic cell which has copper and silver electrodes.
2Ag(s) + Cu2+(aq)⇌ 2 Ag+(aq) + Cu(s)
What is a Galvanic cell?
Galvanic or voltaic cells store electrical energy. Batteries are made from series of galvanic cells to produce a higher voltage. The reactions at the two electrodes in Galvanic cells tend to proceed spontaneously. When the reactions are taking place, there is a flow of electrons from the anode to the cathode via an external conductor. For example, if the two electrodes are silver and copper in a Galvanic cell, the silver electrode is positive with respect to the copper electrode. The copper electrode is the anode, and it undergoes oxidation reaction and release electrons. These electrons go to the silver cathode via the external circuit. Hence, silver cathode undergoes reduction reaction. A potential difference is generated between the two electrodes which allow the electron flow. Following is the spontaneous cell reaction of the above Galvanic cell.
2 Ag+(aq)+ Cu(s)⇌ 2Ag(s) + Cu2+(aq)
What is the difference between Electrolytic cell and Galvanic cell?
• Electrolytic cells need an external electrical energy source for operation, but Galvanic cells operate spontaneously and give out an electric current.
• In an electrolytic cell, the direction of current is opposite of that in the galvanic cells.
• The reactions in the electrodes are reversed in both types of cells. That is in an electrolytic cell the silver electrode is the anode, and the copper electrode is the cathode. However, in Galvanic cells, the copper electrode is the anode, and the silver electrode is the cathode.
• In an electrochemical cell, the cathode is positive, and anode is negative. In an electrolytic cell, the cathode is negative, and anode is positive.
• For the operation of electrolytic cells, a higher voltage is required than the Galvanic cells.