I understand that generating the hydrogen that powers a typical fuel cell is (prohibitively?) energy intensive at this point, but I was curious about the following: Assuming a sufficiently efficient catalyst was obtained that allowed large-scale production of pure hydrogen without environmentally damaging by-products, what is the efficiency, on average, of a hydrogen fuel cell on the scale that would power a car, motorcycle, or even provide most of the electrical needs of the average home? Just curious. Not a homework question, and I hope I have the correct forum area to be posting this question into. Thank you in advance for any help in answering this question for me.