¨Researchers at MIT claim to have invented the first practical "artificial leaf". The playing-card-sized device, when placed underwater in direct sunlight, splits water molecules into oxygen and hydrogen, which could then be stored in a fuel cell to produce electricity. A single leaf, already 10 times more efficient at cleaving H2O than a real one, should provide enough daily power for one house in the developing world. Unlike previous artificial leaves, the new one utilises inexpensive materials: silicon plus nickel and cobalt catalysts.
Considerable challenges remain, though, including figuring out how to capture the gases. – Alex Hutchinson