Does it have to be found in the Chem Lab? I mean, is the character stuck at the school, or can he go on a supply run? The easiest thing around that can be triggered with electricity like a cellphone is a model rocket engine, available at any hobby store in the country. They are basically a firework with a little primer that can be triggered from low voltage device like a flashlight, alarm clock beeper, etc. You wont get into trouble for introducing chemical recipes since there isnt any real mixing/manufacturing involved.
If you need other ideas, recipes, etc, or you have specific scenario restrictions on what he can do, send me a PM. I prepare for the Zombocolypse as a hobby and intellectual exercise, so I know quite a few of the tricks out there.