One of the big problems with hydrogen is it just embrittled metals, eats everything, it is very reactive and caustic, it's so small (an atom)it just leaks and goes through solid metal and other materials, destroying them in the process. The other problem is you still have to make the hydrogen, which itself is an energy intensive process, . It's really kind of a stupid fuel to use when so many other fuels are available. It just looks good as an end product, because people can say they have a zero emissions vehicle, which is a lie