Sustainable Energy

Quantum Dots Make Artificial Photosynthesis Last Longer

Nanoparticles offer a solution to a key problem with splitting water with sunlight to generate hydrogen.

Artificial photosynthesis—splitting water with energy from sunlight—could provide a way to harness and store power from the sun and provide carbon-free fuel for cars.

Using the energy in sunlight together with water and air to make fuel—artificial photosynthesis—is a little closer thanks to an advance involving nanoscale crystals known as quantum dots.

Hydrogen generator: Researchers used this setup to measure hydrogen production facilitated by novel nanoparticles.

Researchers have been working on artificial photosynthesis for many years (see “Sun + Water = Fuel”). One approach involves using particles that combine light-absorbing materials with catalysts that can split water. But the light-absorbing materials tend to deteriorate quickly in sunlight, rendering the approach impractical.

In the latest issue of the journal Science, researchers from the University of Rochester show that quantum dots not only absorb the light but also are far more durable than previous light-absorbing materials. The new approach also has the advantage of not requiring any precious metals, so it might be relatively cheap.

The new approach doesn’t solve all of the challenges with artificial photosynthesis. The proof-of-concept system developed by the Rochester team does only half of the water-splitting reaction—that is, it makes hydrogen, but not oxygen. What’s more, particle-based approaches like this one generate both hydrogen and oxygen in one container, and there’s a danger that they will interact and explode. Alternate approaches to photosynthesis that generate hydrogen and oxygen in separate containers are safer.

The remaining difficulties point to the need for efforts like the Department of Energy Innovation Hub at Caltech. The hub is designed to evaluate advances like this one in light of how they might work in a complete artificial photosynthesis system—and if such approaches look workable, to build and test prototype systems (see “Artificial Photosynthesis Effort Takes Root”).

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