Why would you need to do that? You produce hydrogen via “direct-air electrolysis” and then use it as a fuel by reacting it with oxygen in a fuel cell. Compare

Why would you need to do that? You produce hydrogen via “direct-air electrolysis” and then use it as a fuel by reacting it with oxygen in a fuel cell. Compared to lithium ion batteries it’s just a different chemical medium for storing energy. In practice you’d probably have something like a fuel station producing hydrogen in-situ with energy pulled from the grid.