Synthetic photosynthesis

Wind, solar, hydrogen, algae. They’re all promising new forms of energy. But the future is fake leaves.

As a planet, we seem always able to make more of one thing: pollution. (Two if we count Fast and Furious movies.) Specifically, we make a lot of carbon dioxide. Trees take care of some of that by converting it into carbohydrates they use to grow, but they can’t keep up. So scientists at the universities Caltech, Northwestern, Yale, and Chicago are working on fake leaves that turn sun, water, and carbon dioxide into fuel. The process is called synthetic photosynthesis. Two electrodes are submerged in water. When activated by sunlight, one of the electrodes breaks down the water into oxygen, protons, and electrons. The other electrode assembles the protons and electrons into hydrogen gas. A membrane keeps the two gases separate – otherwise they could explode – before they are pumped off and stored as fuel.

Researchers led by MIT professor Daniel Nocera produced the “artificial leaf”, shown here with real leaves. Like living leaves, the device can turn the energy of sunlight directly into a chemical fuel that can be stored and used later as an energy...