In many electrochemistry scholarly articles/studies they talk about certain specific reactions occurring at certain voltage potentials, while in other articles they talk about current density as the determiner for which reactions happen.
Why is this? From what I know about electrical engineering you can either set the voltage, and the current will adjust accordingly, or you can set the current and the voltage will adjust to meet the current. You cannot set both of them at the same time. That would defy the laws of physics.
So what do many of these articles mean when they talk about, for instance:
Reported reactions of this type often occur at potentials smaller than -3 V
How does this relate to the current density that is set by a power supply for instance?