This needs an expensive catalyser. But the solar energy is free and it generates about a kilogram of hydrogen a day, which can power a car for 150 km. We need green hydrogen to power the whole world and leave the fossil fuels in the ground. Now!
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The European Commission plans on having 500 GW of green hydrogen capacity by 2050. Other countries should be doing the same.
https://www.scientificamerican.com/article/green-hydrogen-could-fill-big-gaps-in-renewable-energy/