Can you have one half-reaction take place, without the other half-reaction taking place immediately?

The other half-reaction takes place when
the cell potential is raised.
I half witness this in some electrochemical cells.
Sincere Thanks.

It wont occur very long, as charge builds up, and will stop the reaction.

Yes, it is possible for one half-reaction to take place without the other half-reaction occurring immediately in an electrochemical cell. This phenomenon is called electrode polarization.

In an electrochemical cell, two half-reactions occur simultaneously at different electrodes, also known as half-cells. One half-reaction occurs at the anode (negative electrode) and involves the oxidation of a species, while the other half-reaction occurs at the cathode (positive electrode) and involves the reduction of a species.

Under normal conditions, the two half-reactions occur simultaneously, allowing the flow of electrons from one electrode to another, resulting in a complete redox reaction. However, in some cases, the occurrence of one half-reaction can be hindered or slowed down, preventing the completion of the overall reaction.

This can happen when there is a high resistance or impedance at one of the electrodes, which can impede the movement of electrons. This resistance could be due to factors such as the formation of a passivating layer on the electrode surface, the accumulation of reaction products, or the presence of impurities.

In such instances, the half-reaction occurring at the electrode with electrode polarization will be delayed or inhibited, while the half-reaction occurring at the other electrode will still proceed normally. This leads to an imbalance in the cell potential, causing an accumulation of charge and an increase in the energy required to drive the reaction forward.

Electrode polarization can be reduced or eliminated by various methods. For example, using a higher potential or increasing the concentration of reactants can help overcome the resistance and allow the hindered half-reaction to proceed. Additionally, applying an external electrical potential across the electrodes, known as overpotential, can overcome the polarization and promote the completion of the overall redox reaction.

It is important to note that electrode polarization can have both negative and positive effects on the performance of electrochemical cells. While it can hinder the cell's efficiency, it can also be utilized in certain applications, such as in corrosion protection or electroplating.

In summary, electrode polarization can cause one half-reaction to occur without the immediate completion of the other half-reaction in an electrochemical cell. This can be overcome by adjusting the potential, reactant concentrations, or applying an external electrical potential.