The Null have some resistance to electricity. It takes a pretty high voltage to affect them, but then they would be stunned and temporarily vulnerable as their systems adjusted.

As for the weapons, they are very technologically advanced - with time and the right knowledge, they could learn about how it works, however. Whether it can be used for good really depends on how it's used, though! It can be used to attack the gods, of course, and it can be used to attack other characters or creatures who are made of energy or magic. While it will affect the Null a little, it won't seriously damage or kill them.