electrochemical cell vs electrolytic cell

3 min read 17-03-2025

electrochemical cell vs electrolytic cell

Electrochemical cells and electrolytic cells are both systems involving chemical reactions and electron transfer. However, they operate in fundamentally opposite ways. Understanding their differences is crucial in electrochemistry. This article will delve into the core distinctions between these two types of cells, exploring their mechanisms, applications, and key characteristics.

What is an Electrochemical Cell?

An electrochemical cell, also known as a galvanic cell or voltaic cell, is a device that generates electrical energy from a spontaneous chemical reaction. This spontaneous reaction involves the transfer of electrons from a higher potential energy state to a lower one. The energy released during this process is harnessed as electrical current.

Key Characteristics of Electrochemical Cells:

Spontaneous Reaction: The underlying chemical reaction occurs naturally without external intervention.
Energy Production: They convert chemical energy into electrical energy.
Positive Cell Potential (E°cell): The standard cell potential is always positive, indicating a spontaneous reaction.
Anode is Negative, Cathode is Positive: Electrons flow from the anode (oxidation) to the cathode (reduction).
Examples: Batteries (like AA, AAA, etc.), fuel cells.

How an Electrochemical Cell Works:

An electrochemical cell consists of two half-cells: an anode (where oxidation occurs) and a cathode (where reduction occurs). These half-cells are connected by an external circuit allowing electron flow and a salt bridge (or porous membrane) facilitating ion movement to maintain electrical neutrality. The electrons flow through the external circuit, creating an electrical current. The salt bridge allows ions to flow between the half-cells, completing the circuit and preventing the buildup of charge that would stop the reaction.

What is an Electrolytic Cell?

An electrolytic cell is a device that uses electrical energy to drive a non-spontaneous chemical reaction. In essence, it's the reverse of an electrochemical cell. It requires an external power source (like a battery or power supply) to force the reaction to proceed.

Key Characteristics of Electrolytic Cells:

Non-Spontaneous Reaction: The chemical reaction requires an external energy source to occur.
Energy Consumption: They consume electrical energy to drive a chemical reaction.
Negative Cell Potential (E°cell): The standard cell potential is always negative, indicating a non-spontaneous reaction.
Anode is Positive, Cathode is Negative: The external power source forces electrons to flow from the cathode to the anode.
Examples: Electroplating, electrolysis of water, production of aluminum.

How an Electrolytic Cell Works:

Similar to electrochemical cells, electrolytic cells have an anode and a cathode. However, the direction of electron flow and the nature of the reactions are reversed. The external power source forces electrons onto the cathode, causing reduction. Simultaneously, electrons are drawn from the anode, causing oxidation. This forced electron flow drives the non-spontaneous chemical reaction.