Based on educated guesses, which one of the following promises a better future for storing energy for grid scale, automobiles etc as opposed to batteries:

1) Fuels synthesized form CO2

2) Hydrogen (Ideally Green or Blue Hydrogen in the long run)

I am debating between which one of these two technologies to choose for my graduate research. My main goal is to help develop an alternative to way to store energy from renewables, an alternative to batteries.

I know the cost of producing fuels from CO2 is relatively high at present and Hydrogen comes with its own unique challenges like embrittlement and a relatively low round-trip efficiency. But considering all of these factors, which one of the two has a better shot getting a wide scale adaptation?

The idea of using CO2 derived fuels in existing infrastructure is appealing. But at the moment, there seems to be push towards Hydrogen in a lot of places, even though the technology is more expensive than batteries at the moment. Would the cost of Hydrogen would eventually come down with economies of scale and R&D?

My concern is that batteries won't be able to offer a large scale energy storage solution and suffers from relatively short life cycles. And also the supply of transition metals used in it won't be assuring once wide adoption picks up.

I would greatly appreciate any feedback or suggestions.

Thanks