Hydrogen could be a great fuel. The smoke from burning hydrogen is water. Not carbon dioxide. It can be made from green energy sources such as solar.
Could fuel vehicles and aircraft, but it's hard to store in a tank. It's so light it doesn't store much energy, unless compressed which is problematic. Gasoline has a lot more energy per volume of storage.
Scientists have been exploring various ways to store more hydrogen in a given "tank" space using various methods. Here's another breakthrough which looks promising. A metal hydride technique.