The Aloe Vera Plant is one of the best plants for indoors that produces the most oxygen and helps to clean the air.
Other good indoor plants that are good at producing quite a bit of oxygen are the weeping pig, snake plant, Peace Lily, Rubber Plant and the Gerbera Daisy plants.
There are some other good indoor plants for oxygen but those above are some of the best indoor plants when you're looking for plants that produce the most oxygen.