Name: voltammetry and faradaic current
Uploaded: 2024-12-05T18:31:57.000Z
Duration: 1 min 21 s
Channel: JoVE

La corriente faradaica es la corriente producida en los electrodos de trabajo y auxiliares debido a la oxidación o reducción de un analito.
La corriente catódica producida por la reducción del analito lleva una carga positiva, mientras que la corriente anódica producida por la oxidación del analito tiene carga negativa.
El flujo de corriente faradaica está gobernado por el potencial aplicado en el electrodo de trabajo, y su magnitud depende de la velocidad de la reacción de oxidación o reducción resultante en la superficie del electrodo.
Los procesos de transporte de masa como la difusión, la migración y la convección afectan a la corriente faradaica al facilitar el movimiento de iones o moléculas desde la superficie del electrodo hasta la solución a granel y viceversa.
La tasa de transporte masivo también influye en la corriente. Si la velocidad de la cinética de transporte de electrones es rápida, la reacción redox está en equilibrio y el sistema es electroquímicamente reversible.
Por el contrario, cuando la velocidad de la cinética de transporte de electrones es lenta, el sistema se trata como electroquímicamente irreversible.
Finalmente, la corriente no faradaica producida por los cambios en el potencial del electrodo debe tenerse en cuenta antes de medir el componente faradaico.

voltamperometría: factores que afectan las mediciones

Voltammetry: Factors Affecting Measurements

La corriente producida debido a las reacciones redox del analito en los electrodos de trabajo y auxiliares se denomina corriente faradaica. La reacción se puede dividir en dos tipos. La corriente generada debido a la reducción del analito se llama corriente catódica y tiene una carga positiva. Por el contrario, la corriente producida por la oxidación del analito se conoce como corriente anódica y tiene una carga negativa. El potencial aplicado en el electrodo de trabajo determina el flujo de corriente faradaica y la magnitud de la corriente farádica depende de la velocidad de la reacción de oxidación o reducción resultante en la superficie del electrodo.

Además, varios procesos de reacción de transporte de masa como la difusión, la migración y la convección afectan a la corriente faradaica al facilitar el movimiento de iones o moléculas desde la superficie del electrodo hasta la solución a granel y viceversa. Durante la difusión, los iones o moléculas se transportan desde una región de alta concentración a una región de baja concentración y el efecto de la difusión sobre la velocidad de transporte de masa depende del tiempo. Se denomina convección si se utiliza un medio mecánico para transportar reactivos hacia el electrodo y retirar productos del mismo. Se denomina migración si las partículas cargadas del analito son atraídas o repelidas por los electrodos.

La velocidad de transporte de masa también influye en la corriente. Si la velocidad de la cinética de transporte de electrones es rápida, la reacción redox está en equilibrio y el sistema es electroquímicamente reversible. Por el contrario, cuando la velocidad de la cinética de transporte de electrones es lenta, el sistema se considera electroquímicamente irreversible. Finalmente, la corriente de carga no faradaica producida por los cambios en el potencial del electrodo debe tenerse en cuenta antes de medir el componente faradaico.

Voltamperometría: factores que afectan las mediciones

Una corriente producida debido a las reacciones redox del analito en los electrodos de trabajo y auxiliares se denomina corriente faradaica. La reacción puede ser ...

voltammetry-factors-affecting-measurements

Education

Educación

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidad 1

Electrochemical Analyses and Redox Titration

Análisis electroquímicos y valoración redox

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

voltammetry and faradaic current

Voltammetry measures faradaic current, which is the current created by redox reactions of an analyte at the working and auxiliary electrodes. The current from reduction is called cathodic current and carries a positive charge. The current from oxidation is called anodic current and has a negative charge.

The applied potential at the working electrode controls the flow of faradaic current. The size of that current depends on how fast the oxidation or reduction reaction occurs at the electrode surface. Mass transport also changes the current because it moves ions or molecules between the electrode surface and the bulk solution.

Diffusion, migration, and convection are the main mass transport processes. Diffusion moves particles from high concentration to low concentration, and its effect changes with time. Convection uses mechanical motion to carry reactants toward the electrode and move products away, while migration happens when charged analyte particles are attracted or repelled by electrodes.

The rate of mass transport also affects the measured current. When electron transport kinetics are fast, the redox reaction stays at equilibrium and the system is electrochemically reversible. When electron transport kinetics are slow, the system is electrochemically irreversible.

A nonfaradaic charging current must also be considered before the faradaic component is measured. This charging current comes from changes in electrode potential. It does not arise from the analyte redox reaction, so it must be separated from the current of interest.

Voltammetry and Faradaic Current

electrochemistry: overview

Electrochemistry and Redox Reactions

Electrochemistry connects electrical measurements with chemical reactions, especially oxidation and reduction. It focuses on how electron movement helps explain reaction behavior. Oxidation is the loss of electrons from a substance, and reduction is the gain of electrons. A species with strong electron affinity is an oxidizing agent, or oxidant. A species that donates electrons is a reducing agent, or reductant. These redox steps are often described with half-reactions. When electrons move...

electrodes: overview

Types of Electrodes in Electrochemistry

Electrodes are conductive materials in an electrochemical cell. They allow electron transfer reactions to happen at their surfaces. Electrochemical measurements use them to control and measure current and potential. The working electrode, also called the indicator electrode, is the main sensing electrode. Its potential changes with the analyte concentration and with the activity of the electroactive species. Common indicator electrodes include inert platinum electrodes, silver electrodes that...

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Static and dynamic electrochemical methods study what happens at the boundary between an electrode and a solution. These interfacial methods focus on the electrode-solution interface rather than the overall properties of the liquid. They are useful in electroanalytical chemistry because they can detect very small changes in analyte concentration. These methods are grouped by whether a nonzero current flows through the cell. Static methods, such as potentiometry, measure the cell potential...

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Reference and Indicator Electrodes in Potentiometry

Potentiometric measurements use reference electrodes and indicator electrodes to track changes in a solution. A reference electrode gives a stable baseline, while indicator and working electrodes respond to changes in the solution’s composition. The Standard Hydrogen Electrode, or SHE, is a common reference electrode. It keeps a zero potential at all temperatures. However, it needs a continuous supply of hydrogen gas, so it is not practical for routine use. The Saturated Calomel Electrode, or...

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redox titration: overview

Redox Titration Endpoints and Indicators

Redox titration uses electron transfer in a redox, or reduction-oxidation, reaction to find the concentration of an unknown solution. The titrant has a known concentration, and it is added gradually to the analyte, which is the solution being tested. The endpoint shows when the reaction between the two substances is complete. Before a redox titration begins, the analyte should be in a single oxidation state. If needed, this is done by pre-oxidizing or pre-reducing the sample with an auxiliary...

redox titration: iodimetry and iodometry

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redox titration: other oxidizing and reducing agents

redox-titration-other-oxidizing-and-reducing-agents

Choosing Oxidizing Titrants in Redox Titration

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Endpoint Detection in Potentiometric Titration

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Controlled-Current Coulometry in Redox Analysis

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voltammetry: factors affecting measurements

Voltammetry measures faradaic current, which is the current created by redox reactions of an analyte at the working and auxiliary electrodes. The current from reduction is called cathodic current and carries a positive charge. The current from oxidation is called anodic current and has a negative charge. The applied potential at the working electrode controls the flow of faradaic current. The size of that current depends on how fast the oxidation or reduction reaction occurs at the electrode...

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Voltammogram Shapes and Redox Analysis

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Polarography and Voltammetry with Mercury Drops

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Pulse Voltage Methods for Electrochemistry

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voltammetric-techniques-cyclic-voltammetry

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Measuring Analytes with Amperometric Sensors

Amperometry measures specific analytes in a solution by tracking the electric current from an electrochemical reaction. A constant potential is applied between a working electrode and a reference electrode. The current that results is proportional to the analyte concentration. The Clark oxygen electrode is a common example of amperometry. It uses a cathode and an anode sealed inside a gas-permeable membrane. The cathode is typically platinum or gold, and the anode is silver. When a potential...

key terms and concepts

Learn how faradaic current in voltammetry depends on redox reactions, mass transport, electron-transfer rate, and charging current at the electrodes.

Voltammetry and Faradaic Current | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Voltammetry and Faradaic Current

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