Liquid hydrocarbon fuels from the sun and air. Point: with liquid fuels being 20-60 more energy dense, it is likely that liquid hydrocarbon fuels will be with us for ever. Unless we go to hydrogen.
At 2:02 in the video, there is an excellent animation of the basic chemistry of Cerium Oxide. Cerium is more electropositive than the co2 and h20 it reacts with - so the oxygen is stripped from the reactants to make carbon monoxide and hydrogen. Which can then be turned to fuels.