On this page of our guide to Batman: Arkham Knight you will find out how to unlock the Freeze Blast, which is one of the Batman gadgets. It's required to get some of the secrets hidden in the game.
The Freeze Blast is a unique gadget, the possession of it is required for completing some of the secrets in the movie studio. You don't gain it during the completing the main story, but getting it, fortunately, is very simple. Go to the Quarantine Area, the big room which is close to the way out from the movie studio. In that room there are several cells in which Batman keeps/used to keep the infected Jokers. The gadget you are looking for is on the small table, next to the cell on the left, as shown on the picture.