Missing: ammonia. This is an interesting candidate as an electrofuel, though all the contenders have drawbacks. Ammonia is nasty stuff if it spills, and like all synfuels other than hydrogen itself, it requires an expensive additional reforming step.

It has two big advantages:
– unlike methane, ammonia is not a GHG;
– it has a high boiling point, between those of propane and butane; like them it can either be transported as a gas in pipelines at ambient temperature, or stored as a liquid in cheap steel vessels, again at ambient temperature. Hydrogen and methane both require very expensive refrigeration equipment to reach the liquid state.
Japan and Australia are both working on ammonia as a synfuel, for example in shipping.