Heim » Overpotential (chemistry)

Overpotential (chemistry)

1910
  • Julius Tafel

Overpotential is the potential difference (voltage) between a half-reaction’s thermodynamically determined reduction potential and the potential at which the redox event is experimentally observed. It represents the extra energy required to overcome activation barriers for the electrode reaction to proceed at a significant rate. It is a key factor in the energy efficiency of all electrolytic processes.

In an ideal electrolytic cell, the applied voltage needed to drive a reaction would be exactly equal to the cell’s standard electrode potential ([latex]E^0_{cell}[/latex]). However, in reality, a significantly higher voltage is almost always required. This excess voltage is the overpotential ([latex]\eta[/latex]). The total cell potential ([latex]E_{cell}[/latex]) is the sum of the equilibrium potential, the overpotentials at both electrodes, and the ohmic drop (IR drop) across the electrolyte: [latex]E_{cell} = E^0_{cell} + \eta_{anode} + \eta_{cathode} + IR_{drop}[/latex].

Overpotential arises from several sources. Activation overpotential is related to the kinetics of the electron transfer step at the electrode surface itself. Some reactions, like the evolution of hydrogen or oxygen gas, have inherently slow kinetics and require a large activation overpotential. Concentration overpotential occurs when the concentration of reactants at the electrode surface differs from the bulk concentration due to slow diffusion. Resistance overpotential is caused by the resistance of the electrolyte or films on the electrode surface.

The relationship between current density (j) and activation overpotential is often described by the Tafel equation: [latex]\eta = a + b \log(j)[/latex], where ‘a’ and ‘b’ are constants (Tafel parameters) specific to the electrode reaction and material. This equation shows that to get a higher reaction rate (higher current density), a larger overpotential is required. The primary goal in designing efficient electrochemical systems is to minimize overpotential, which is typically achieved by using electrocatalysts (materials that lower the activation energy), increasing the operating temperature, or optimizing the electrode structure to enhance mass transport.

UNESCO Nomenclature: 2406
– Electrochemistry

Typ

Physical Phenomenon

Disruption

Substantial

Verwendung

Widespread Use

Precursors

  • Nernst equation describing equilibrium electrode potentials
  • Arrhenius equation relating reaction rate to activation energy
  • development of the concept of chemical kinetics
  • Faraday’s laws of electrolysis

Anwendungen

  • designing efficient industrial electrolyzers (e.g., for hydrogen production)
  • developing better catalysts to reduce energy loss in fuel cells
  • understanding and preventing corrosion
  • improving the performance of batteries during charging
  • optimizing electroplating processes for uniform coatings

Patente:

DAS

Potential Innovations Ideas

!Professionals (100% free) Mitgliedschaft erforderlich

Sie müssen ein Professionals (100% free) Mitglied sein, um auf diesen Inhalt zugreifen zu können.

Jetzt teilnehmen

Sie sind bereits Mitglied? Hier einloggen
Related to: overpotential, electrolysis, electrochemistry, Tafel equation, activation energy, voltage efficiency, electrocatalysis, current density

Schreibe einen Kommentar

Deine E-Mail-Adresse wird nicht veröffentlicht. Erforderliche Felder sind mit * markiert

VERFÜGBAR FÜR NEUE HERAUSFORDERUNGEN
Maschinenbauingenieur, Projekt- oder F&E-Manager
Effektive Produktentwicklung

Kurzfristig für eine neue Herausforderung verfügbar.
Kontaktieren Sie mich auf LinkedIn
Integration von Kunststoff-Metall-Elektronik, Design-to-Cost, GMP, Ergonomie, Geräte und Verbrauchsmaterialien in mittleren bis hohen Stückzahlen, regulierte Branchen, CE und FDA, CAD, Solidworks, Lean Sigma Black Belt, medizinische ISO 13485

Wir suchen einen neuen Sponsor

 

Ihr Unternehmen oder Ihre Institution beschäftigt sich mit Technik, Wissenschaft oder Forschung?
> Senden Sie uns eine Nachricht <

Erhalten Sie alle neuen Artikel
Kostenlos, kein Spam, E-Mail wird nicht verteilt oder weiterverkauft

oder Sie können eine kostenlose Vollmitgliedschaft erwerben, um auf alle eingeschränkten Inhalte zuzugreifen >Hier<

Historical Context

(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)

Related Invention, Innovation & Technical Principles

Nach oben scrollen

Das gefällt dir vielleicht auch