# Using a calcium metal anode in aqueous solution?

In school, I am doing an electrochemistry lab in which I need to create a galvanic cell battery with the highest voltage possible using two beakers, a salt bridge, and electrodes.

To maximize the voltage, I have decided to use calcium metal for the oxidation half-reaction and a sodium persulfate solution for the reduction half-reaction. I understand that for the reduction reaction in the cathode, I would merely dissolve the persulfate in water. However, calcium metal reacts with water, so how would I go about connecting the calcium to the salt bridge (which is a requirement in the lab)?

The salt bridge has an aqueous salt and my chemistry teacher said that the redox reaction that would result from letting the calcium touch the water would prevent it from being effective in the battery. Also, my class vaguely touched on the Nernst equation, but are there any other revisions I can make to the battery to increase the voltage, either by adding $\ce{OH-}$, $\ce{H+}$, or increasing/decreasing concentration of the persulfate solution?

Calcium does react with water, but it does so slowly especially in cold water. You should be able to use it as you would a typical metal as some water will touch the metal. Just be aware that it will react and your voltage may be less than predicted. This battery of course would be of no practically use as its shelf life would be on the order of less than an hour, but should last long enough to obtain a measurement and complete the experiment. You should also expect to see a change in voltage over time as $\ce{Ca(OH)2}$ is added to solution reducing the potential.