What kind of engineer would work on the hydrogen fuel cell?

Basically, any degreed engineer will have the fundamental knowledge of chemistry, physics and thermodynamics to begin learning about hydrogen fuel cells.

However, the experts who are at the leading edge of this field will have advanced knowledge of an area of study that is known as Energy Engineering. This involves thermodynamics, chemistry and combustion processes.

If you are looking for a bachelor degree program, mechanical engineering would probably be the right major. Then, you could specialize in fuel cells in graduate school.