The biggest advantage of hydrogen is that it produces no carbon emissions. Are there any other advantages?

Green electricity is made by windmills and solar panels. However, you can only store these electrons in batteries to a limited extent and they are also difficult to transport. Molecule storage is much easier and cheaper and the energy content will stay the same throughout time. It is also possible to refuel much more quickly.

Hydrogen is the most basic molecule you can make with green energy, making it the most energy efficient conversion, and the first step for any other alternative like ammonia or even methanol.

Hydrogen is abundantly available both on earth and in space, yet de facto mainly extractable from water. Hydrogen is reconverted into water once it has reacted with oxygen. You can keep doing the process of splitting (in an electrolyser) and oxidation (by combustion or by an electro-chemical reaction in a fuel cell) indefinitely. Even the water from the ocean can be used to make hydrogen. So there is an abundance of water available. And after reaction, the water will simply fall from the sky as rain, after which it can be converted into hydrogen again via an electrolyser with green electricity. This makes hydrogen a sustainable and scalable molecule for energy-usage that does not need any carbon involved.