"inner passion" is correct and usable in written English.
You can use it to describe a strong emotion for something, such as a person, idea, or project. For example, "He had an inner passion to help others in need."
He skips work and follows his inner passion for antiquing.
Somehow Richards with that burning inner passion just willed himself to succeed.
Entrepreneurs start from that place we call Heart, inner passion and desire that is not easily malleable.
Heart — e.g. inner passion and purpose — is the strongest and most important trait among the business founders we surveyed.
The eye-popping setting is the work of Ronald Bricke, an interior designer who channeled Ms. Heckler's inner passion for boldness.
Mr. Bush favors a bipartisan approach on these issues, but his proposals have seemed reactive rather than driven by an inner passion.
Through interlaced scenes, each saturated with emotion, he uncovers the inner passions of his characters.
Patrick was charming, graceful and seemingly impassive; he rarely showed his inner passions.
As professor of education at Warwick University, Dr Robinson led a national commission on creativity, education and the economy for the British government, and has spent the past decade trying to prevent education authorities from stifling their students' inner passions.
With such violence in these characters' internal worlds, and such a maddening external impassiveness, those inner passions are bound to break out somehow, and it won't be pretty.
In the Zeffirelli staging principal performers are called on to convey turbulent inner passions against a backdrop of Disneyesque constructions, while competing with milling crowds, cavorting children, flamenco dancers and a mobile menagerie of horses, donkeys and dogs.
