What's the actual point of doing this? This is another sneaky fossil fuel "idea" that just wants to make sure their product is still required in the electrified future. Hydrogen isn't an energy source, it's a storage medium. It compares poorly to batteries is a variety of use cases, fuel cells can be a consumable component, and you have to deal with storing the hydrogen before you convert it to electricity or burn it (have fun assembling all of those parts for a combustion engine).

I get it - it's cool science and there's probably a couple of edge cases or whatever where this does make sense, but solar panels, batteries, and electric motors are all here and mostly work. The technology for all of that will continue to get better and make any hydrogen use cases even less practical. Just leave the oil in the ground.

In this case hydrogen is an energy source. You split CH4 into C and 2H2, put the solid carbon in some storage, and either burn the hydrogen in a regular power plant, or you put it in a fuel cell. Either way, you generate electricity. With methane pyrolysis, hydrogen is not a storage medium, it becomes a regular fuel.

> What's the actual point of doing this?

Hydrogen is heavily used industrially, and today the most common and economical way it is produced is via steam reforming of methane, which emits CO2 as a byproduct. This method has the benefit of outputting solid carbon instead of CO2 while still being economically viable unlike most other ways of generating hydrogen.