Do volcanoes contribute to ozone depletion?

You need to study "ozone depletion" and form an opinion about whether any such thing exists. Then you can study the alleged causes of such a thing and decide whether those allegations are valid and true. (For instance the theoretical chemistry may be valid, but it may or may not have been established that any human activity has produced enough pollution at the necessary altitude to sustain such reactions.) Then you have to determine whether volcanoes produce that pollution.

Professional people have studied this topic a lot and they are not entirely sure about any part of it, but all their chemistry depends on chlorine and volcanoes are not known to be a source of chlorine.