Scientists Create Molecule That Brings Artificial Photosynthesis Closer to Reality

Scientists at the University of Basel have developed a specially designed molecule that could play a pivotal role in artificial photosynthesis – a process aimed at turning sunlight into sustainable fuels. The innovation, published in Nature Chemistry, allows the molecule to store two positive and two negative charges under light, mimicking the charge separation that occurs in plants.

Photosynthesis in nature uses sunlight to convert carbon dioxide into energy-rich sugars, fueling life on Earth. Researchers are striving to replicate this process to produce solar fuels such as hydrogen, methanol, and synthetic petrol – energy sources that would be carbon-neutral when burned.

The molecule, designed by a team of chemists, consists of five parts: a central unit that absorbs sunlight and two pairs of components on each side that act as electron donors and acceptors. When sunlight hits the molecule, it triggers the transfer of electrons from one side to the other, generating positive and negative charges internally.

This stored energy can then be used to split water into hydrogen and oxygen, producing clean hydrogen fuel. Unlike fossil fuels, which take millions of years to form from ancient plants and animals under intense pressure and heat, this artificial process captures solar energy instantly and emits no carbon dioxide when the hydrogen is used.

To build up the necessary four charges, researchers used two light flashes in sequence. Each flash generates a positive and a negative charge, which migrate to opposite ends of the molecule. “This stepwise excitation enables the use of significantly dimmer light, approaching the intensity of sunlight,” explains doctoral researcher Mathis Brändlin. The stored charges remain stable long enough to drive chemical reactions, such as splitting water into hydrogen and oxygen. Previously, strong laser light was required for similar experiments, which was a far cry from the vision of artificial photosynthesis.

While this breakthrough doesn’t yet constitute a fully functional artificial photosynthesis system, project lead Professor Oliver Wenger sees it as an essential piece of the puzzle. “We have implemented a key mechanism to better understand electron transfers central to artificial photosynthesis,” he says. “Our goal is to contribute to new pathways for a sustainable energy future.”

Source: University of Basel