At a time of ecological transition, it is clear that hydrogen does not share the same enthusiasm as electric in transport. What's the cause ?
The number of hydrogen vehicles and stations is not growing as fast as electric. This is linked to the fact that hydrogen, although present everywhere in our environment, is very difficult to produce and store for use as fuel.
You should know that today, more than 95% of the 70 million tonnes of hydrogen synthesized in the world each year come from fossil fuels. A reaction called "steam reforming" has the consequence of producing 9 kg of CO² to produce 1 kg of hydrogen.
The other option is to use electricity, especially renewable. But it takes a lot of energy and only 50% of it is converted into hydrogen. This technique uses so-called proton exchange membranes and new prototypes are being researched. A laboratory is in the process of developing a new membrane that transforms 90% of the electricity but for the moment the researchers are far from this figure in practice.
To this is added the compression phase for storage (several hundred times the atmospheric pressure) which again requires energy.
So for all these reasons, hydrogen is not a green fuel but future research could make it ecological.