I can't think of any and google has not been helpful.
Voiceless vowels are quite possible, and occur in one way or another in many languages.
However, the overwhelming majority of vowel sounds in speech are voiced, since vowel formants are modifications of a voiced airstream from the larynx. Exceptions to this rule fall into a number of categories.
Yes, it's technically possible, but I think you'd only consider it as an allophone, otherwise, the better transcription might be /h/. Wikipedia lists one example in English as potato, where the first o is not vocalized, but otherwise the mouth is in the same position and there is air flowing. (IPA transcriptiond use a ring for devoicing).
Japanese seems to the more common language for it with their u vowel, but thinking about, European Portuguese might well do it where traditionally transcriptions will normally list them as elided.
For an academic citation, here's an article on devoiced vowels in English and German.