2.2 Types of Electrochemical Cells
2 min read•july 23, 2024
Electrochemical cells are the workhorses of energy conversion. Galvanic cells, like , turn chemical energy into electricity. Electrolytic cells do the opposite, using electricity to drive chemical reactions.
These cells have key components: electrodes for redox reactions, electrolytes for ion flow, and salt bridges for charge balance. Understanding their types and operations is crucial for harnessing electrochemical power in various applications.
Types of Electrochemical Cells
Galvanic vs electrolytic cells
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- Galvanic cells convert chemical energy into electrical energy through spontaneous redox reactions (batteries, )
- Electrons flow from the to the through an external circuit generating usable electrical current
- Electrolytic cells convert electrical energy into chemical energy by driving non-spontaneous redox reactions (, )
- An external power source forces electrons to flow from the cathode to the anode enabling desired chemical transformations
Components of galvanic cells
- Electrodes serve as sites for redox reactions
- Anode undergoes oxidation releasing electrons into the external circuit
- Cathode undergoes reduction accepting electrons from the external circuit
- Electrolytes are ion-containing solutions that enable electrical current flow
- surrounds the anode while surrounds the cathode
- connects the two half-cells allowing ion flow to maintain charge balance without mixing the electrolytes
Operation of electrolytic cells
- External power source supplies electrical energy driving non-spontaneous redox reactions
- Reduction occurs at the cathode where electrons are supplied
- Oxidation occurs at the anode where electrons are removed
- Electroplating deposits a thin metal layer onto a conductive surface
- Object to be plated is placed at the cathode
- Metal ions in the are reduced and deposited onto the object
- Electrolysis decomposes compounds using electrical energy
- Water electrolysis produces (H2) at the cathode and (O2) at the anode
Fuel cells vs concentration cells
- Fuel cells generate electricity by oxidizing a continuously supplied fuel (H2, methanol)
- Produce water and heat as byproducts
- Used for power generation and transportation
- Concentration cells generate electricity from a concentration gradient between two half-cells
- No net chemical reaction occurs
- Measure species concentrations or study membrane permeability
Key Terms to Review (23)
Anode: The anode is the electrode where oxidation occurs in an electrochemical cell, serving as the site for the loss of electrons during the redox reaction. This term is crucial in understanding various electrochemical systems, as it plays a key role in the flow of electrons and the overall functioning of batteries and fuel cells.
Anolyte: Anolyte is the electrolyte solution found in the anode compartment of an electrochemical cell, where oxidation reactions occur. It plays a crucial role in facilitating the movement of ions, helping to maintain charge balance and allowing for the flow of current. The composition of the anolyte can significantly impact the efficiency and performance of the electrochemical cell.
Batteries: Batteries are electrochemical devices that convert chemical energy into electrical energy through redox reactions. They consist of one or more electrochemical cells, where each cell includes an anode, a cathode, and an electrolyte. The design and materials used in batteries significantly impact their efficiency, energy density, and performance, making them crucial in various applications such as portable electronics and electric vehicles.
Cathode: The cathode is the electrode in an electrochemical cell where reduction occurs, meaning it gains electrons. This process is essential for battery operation, fuel cells, and other electrochemical systems, as it directly impacts energy transfer and storage.
Catholyte: A catholyte is the electrolyte solution that is present in the cathode compartment of an electrochemical cell, where reduction reactions take place. This term connects to the fundamental operations of electrochemical cells, where the catholyte supports the movement of ions and helps facilitate the overall electrochemical processes by providing a medium for charge transfer.
Cell Potential: Cell potential, also known as electromotive force (EMF), is the measure of the ability of an electrochemical cell to produce an electric current. It reflects the difference in potential energy between the oxidation and reduction reactions occurring within the cell, impacting the efficiency and direction of electron flow. A higher cell potential indicates a greater driving force for the electrochemical reaction, which is crucial in understanding the behavior and performance of various electrochemical systems.
Concentration cell: A concentration cell is a type of electrochemical cell that generates an electromotive force (EMF) due to a difference in concentration of ions in two half-cells that are connected by a conductive medium. This setup allows for the spontaneous movement of ions from an area of higher concentration to one of lower concentration, resulting in a flow of electrons and the production of electrical energy. Understanding concentration cells is essential when looking at concepts like membrane potentials, cell notation, and different types of electrochemical cells.
Electrolysis: Electrolysis is a process that uses an electric current to drive a non-spontaneous chemical reaction, typically involving the decomposition of compounds into their constituent elements. This process occurs in an electrolytic cell, where electrical energy is converted into chemical energy to facilitate reactions that would not occur naturally. It plays a crucial role in various applications, including the synthesis of materials, modification of surfaces, and electroanalytical methods for detecting and analyzing substances.
Electrolyte: An electrolyte is a substance that produces ions when dissolved in a solvent, allowing the solution to conduct electricity. Electrolytes are crucial in various electrochemical systems as they facilitate the movement of ions, which is essential for processes like battery operation, fuel cells, and electrolysis.
Electrolytic cell: An electrolytic cell is an electrochemical cell that uses electrical energy to drive a non-spontaneous chemical reaction. In this type of cell, an external voltage source forces the flow of electrons through an electrolyte, resulting in chemical changes at the electrodes. This concept is crucial in understanding various electrochemical processes, including the manipulation of electrode potentials, the calculation of cell efficiencies, and the thermodynamic relationships governing these systems.
Electroplating: Electroplating is a process that uses electrical current to deposit a layer of metal onto a surface, enhancing its appearance, corrosion resistance, and other properties. This technique is critical in various applications, allowing for the production of metal coatings on objects to improve durability and aesthetic appeal. By understanding the principles behind electroplating, one can appreciate how it connects with laws governing electrolysis, different types of electrochemical cells, industrial processing methods, and emerging technologies in the field.
Faradaic Efficiency: Faradaic efficiency refers to the ratio of the actual amount of product formed at an electrode during an electrochemical reaction to the theoretical amount that could be produced based on the charge passed through the cell. This concept is crucial in evaluating the performance of electrochemical cells, especially in applications like energy storage and conversion, as it indicates how effectively electrical energy is converted into chemical energy.
Faraday's Laws of Electrolysis: Faraday's Laws of Electrolysis describe the relationship between the amount of substance transformed during electrolysis and the quantity of electric charge passed through the system. These laws are foundational in understanding how electrochemical processes work, including the principles behind different electrochemical cells, redox reactions, and practical applications like electroplating and voltammetry.
Fuel cells: Fuel cells are electrochemical devices that convert chemical energy from fuels directly into electrical energy through an electrochemical reaction. This process typically involves hydrogen and oxygen, producing electricity, water, and heat as byproducts, making them an important technology for clean energy applications.
Galvanic cell: A galvanic cell is an electrochemical device that converts chemical energy into electrical energy through spontaneous redox reactions. It consists of two electrodes, an anode and a cathode, immersed in electrolyte solutions, allowing for the flow of electrons and ions, thus generating an electric current.
Hydrogen gas: Hydrogen gas (H₂) is a colorless, odorless diatomic molecule that is the simplest and most abundant element in the universe. It plays a crucial role in electrochemical cells, particularly in fuel cells and electrolysis processes, where it acts as a key reactant for generating energy or producing other substances.
Le Chatelier's Principle in Electrochemistry: Le Chatelier's Principle states that if a system at equilibrium is disturbed by an external change, the system will adjust itself to counteract that disturbance and restore a new equilibrium. In electrochemistry, this principle can be applied to predict how changes in concentration, temperature, or pressure will affect the direction of an electrochemical reaction, particularly in types of electrochemical cells where reactions are reversible.
Nernst Equation: The Nernst Equation is a fundamental relationship in electrochemistry that allows the calculation of the electromotive force (EMF) of an electrochemical cell under non-standard conditions. It connects the concentration of reactants and products to the cell potential, providing insights into how changes in concentration and temperature affect electrode potentials and overall cell behavior.
Overpotential: Overpotential refers to the extra voltage that must be applied to an electrochemical cell beyond the theoretical value to drive a reaction at a certain rate. This concept is critical because it affects the efficiency of electrochemical processes, impacting reaction rates, energy consumption, and the overall performance of electrochemical systems.
Oxidation-reduction: Oxidation-reduction, commonly referred to as redox, is a type of chemical reaction where electrons are transferred between substances, leading to changes in their oxidation states. In these reactions, one substance undergoes oxidation (loses electrons) while another undergoes reduction (gains electrons). The balance of these processes is crucial in various electrochemical applications, as they dictate the behavior of different types of electrochemical cells and illustrate how half-cell reactions operate.
Oxygen gas: Oxygen gas is a diatomic molecule composed of two oxygen atoms, represented chemically as O₂. It plays a crucial role in various electrochemical processes, particularly in redox reactions and as a reactant in fuel cells, which convert chemical energy into electrical energy. Understanding its behavior in electrochemical cells is essential for exploring how it contributes to energy conversion and storage technologies.
Salt bridge: A salt bridge is a component used in electrochemical cells that allows the flow of ions between the two half-cells while preventing the mixing of the different solutions. It typically consists of a gel or a tube filled with a salt solution, such as potassium nitrate, which maintains electrical neutrality by allowing positive ions to migrate to the cathode and negative ions to the anode. This helps sustain the flow of electric current by completing the circuit within the electrochemical cell.
Spontaneous reaction: A spontaneous reaction is a chemical process that occurs naturally under specific conditions without the need for continuous external energy input. These reactions are often characterized by a decrease in free energy, indicating that the products are more stable than the reactants. The tendency for a reaction to be spontaneous is closely linked to thermodynamic principles and the types of electrochemical cells, as it determines whether a reaction can happen on its own.