PROBLEM: Every day, plants, algae, and bacteria generate more energy than all the world's power plants, using sunlight to split water into hydrogen and oxygen and then storing the energy in sugar molecules. Artificial photosynthes­is--the process of using solar power to split water through the creation of chemical bonds, as plants do--holds promise as a clean, cheap source of hydrogen to power fuel cells. But to make the process practical, researchers must find catalysts to decrease the amount of energy needed.

SOLUTION: Most attempts at artificial photosynthesis try to split water with a single powerful chemical reaction. Theodore Betle­y, an assistant professor of chemistry and chemical biology, has come up with a method that mimics the multistep process plants use. He arranges small clusters of metals inside a molecular scaffold; the clusters work like a plant's photosynthetic chloroplasts, splitting water molecules in a stepwise fashion that uses less energy than one big reaction. Betley has shown that he can split water using such complexes, but his team is still searching for more-efficient catalysts. If they succeed, they will have found a valuable route to hydrogen for fuel cells by mimicking three billion years of evolution.