Muls from the Dark Sun setting are half dwarves. They’re sterile so I guess maybe they don’t count?

Ia! Shub Niggurath

Iirc the energy required to break down water into hydrogen and oxygen is greater than what burning the mixture produces, but in theory solar power might be a viable option to a certain extent.

Efficiency/viability would probably be nonexistent without some sort of miracle catalyst for the breakdown process.