I see only the potential model been used, without the electrochemistry part. All it does is it solves an extra potential equation which won't have an effect on the fluid flow unless you have Joule heating option on, which you don't. So whatever divergence comes from either the VOF model or species transport. A good first step would be to troubleshoot them one by one: start with VOF model only without surface tension, turn off the poential and species transport, and check if it works. We have a good example illustration a VOF setup on our Ansys Innovation Courses site:
https://courses.ansys.com/index.php/courses/fluid-statics/lessons/simulation-examples-homework-and-quizzes-3/topic/simulation-example-u-tube-manometer/
Note that an initial patch of the secondary (gaseous phase in your case) in a region where the seondary phase is first expected to appear is recommended for a better start up of the simulation.
Once the VOF simulation going, add complexity as needed.
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