A lot of sources explain the concept of the Open-Circuit Potential as simple as the voltage measured when no current flows through the cell, but... What kind of valuable information can be obtained measuring the OCP? How can this information be used to explain the electrochemical phenomena inside the cell? Why could it be important to analyze the OCP of an electrochemical cell before applying an external voltage or current?
As you have already mentioned the definition, let's take an example of electrochemical corrosion where OCP of an electrode reflects the thermodynamic parameter which guides us about the thermodynamic tendency of that metallic materials to participate in the electrochemical corrosion with the electrolyte or neighboring medium. Therefore, a potential below OCP is more thermodynamically stable (less tendency to take part in corrosion) whereas the potential above OCP is considered as thermodynamically unstable and prone to corrosion.
As you have already mentioned the definition, let's take an example of electrochemical corrosion where OCP of an electrode reflects the thermodynamic parameter which guides us about the thermodynamic tendency of that metallic materials to participate in the electrochemical corrosion with the electrolyte or neighboring medium. Therefore, a potential below OCP is more thermodynamically stable (less tendency to take part in corrosion) whereas the potential above OCP is considered as thermodynamically unstable and prone to corrosion.
I agree with the opinion of Sujioy Sarkar where Open Circuit Potential is important since the metal with the low open potential will dissolve faster in the electrolyte than the metal with high open circuit potential.
OCP is equal to the electrochemical potential of the solution. If you apply the potential higher than OCP, you will oxidize the "solution" to the new OCP equal to the applied potential. The similar is valid when if you apply the potential lower than OCP.
OCP of an electrode is equial to thermodynamic potential of electrochemical reaction (in other, electrical units). Therefore the deviation of the value of the circuit voltage from OCP is a measure of the nonequilibrium of the passing electrochemical process under current. Look at Tafel equation, pls.
Dear Raul Marquez,
your question is about the OCP[1-3] (open circuit Potential) or, rather, the OCV[1] (open circuit Voltage) ?
1. https://www.researchgate.net/post/Galvanic_Cells_Open_Circuit_Potential_Equilibrium_Potential_Standard_Potential_Lets_discuss_about_differences
2. https://www.researchgate.net/post/What_kind_of_findings_we_can_deduce_from_open_circuit_potentials
3. The open circuit potential for my coating is +4.9V. Should I believe it? http://egmont.com.pl/gamry/noty/FAQ-My%20Open%20Circuit%20voltage%20is%205%20volts.pdf
After applying the OCP for a certain period, is the electrode polished then put corrosion inhibitor then start the measurement?@
The OCP can give information about the redox state of species in the bulk solution as well as the concentration of different species when the solution contains a mixture.
In my opinion, the difference between chmistry,i.e., materials in vaccum or in air, & electrochemistry,i.e., materials submereged in aqueous solutions, is that materials in aqueous solutions normally develop a potential cross the interface between the materials surface & the electrolytes. This potential is called the open circuit potential or the corrosion potential. Therefore, role of the open circuit electrode potential (OCP) graph versus ,in corrosion test ,is important for indicating how stable the materials in the electrolytes.
OCP in very complex or "multiphase"[1] electrodes (corrosion, etc.) has a "forbidden" (hidden, important, "noisy"[1]) parameter: the kinetics aspect.
1. https://www.researchgate.net/post/How_can_I_fit_the_Inductor_in_electrochemical_impedance_spectroscopy#view=5b1054471a5e7629c36357df
Analyze the OCP of an electrode in electrochemical cell to minimize the influence of the test on the metal-coating system while still obtaining a reliable response.
OCP shows the relationship between the electrode potential and the immersion time, indicating the stability of the sample in the electrolyte
It is the potential of the electrode at which the cathodic and anodic reaction rates are in equilibrium in the absence of applied potential in a given corrosive environment. The metallic materials with nobler OCP are more thermodynamically stable than materials with less noble OCP. Thus, the potential below OCP is more thermodynamically stable (shows less tendency to participate in the corrosion reactions) whereas the potential above OCP is considered thermodynamically unstable and susceptible to corrosion
- Badges
- Science topic
- Similar topics
- Chemistry
- Electrochemistry