Stable Positive Ion Gas Molecule Needed

Hi,

I am working on a project and need a stable positive gas ion.

The conditions would be from roughly -40C to +85C, and the container
would contain carbon aerogel for one electrode and a conductive metal
for the other electrode.

I need a smaller molecule that has the positive charge (protons)
centralized in the middle of it with an electron cloud surrounding it
(not a dipole type of molecule), and one that is stable, that would
not pick up electrons and become neutralized.

Also one that is relatively non-toxic and non-reactive, so if it
leaked out it wouldn't kill anyone around, or eat up anything it came
into contact with.

Is there a good gas that could work for this?

Thanks,

Roger
.