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Breakthrough in Artificial Photosynthesis Could Boost Solar Future


Published Apr 11, 2012

Researchers at the KTH Department of Chemistry have designed a molecular catalyst able to convert water into oxygen and protons at speeds similar to natural photosynthesis. The rapidly advancing field could lead to more efficient solutions for converting and storing solar energy.

Licheng Sun, Professor of Organic Chemistry at KTH.

It’s been many millions of years since green plants acquired the ability to convert energy from sunlight into electrochemical energy through photosynthesis. And for at least three decades, scientists in Europe, the United States and Japan have studied laboratory replication of the process plants use to directly harness solar energy for growth. This research has shown only partial success, with different teams finding various ways to mimic photosynthesis but none able to design a solution that splits water into oxygen and hydrogen fast enough to be of much practical use.

Now a group of researchers at KTH have set a speed record for artificial photosynthesis. “The bottleneck for artificial photosynthesis has always been getting the process to go fast enough,” says Licheng Sun, Professor of Organic Chemistry.

Sun’s research group has hit upon a more efficient molecular catalyst that reaches a “turnover frequency” as high as 300 oxygen molecules per second per catalyst, comparable to the natural rate of 100 to 400 molecules per second. “It’s definitely a world record and an important breakthrough for molecular catalysis in artificial photosynthesis,” Sun says. 

Splitting water into oxygen and hydrogen at speeds approaching nature’s own could provide a significant boost for alternative energy sources that don’t contribute to the atmospheric carbon load believed to be causing climate change.

Sun points to the soaring price of oil as a critical driver in the race to identify rapid molecular catalysts. Continued progress in the field could make it possible to convert carbon dioxide into carbon-based fuels such as methanol, and related technologies can directly convert solar energy into hydrogen gas for use in emerging fuel cell applications. He adds that he and his colleagues are focussed on research to help make the new technology cost-competitive.

“This speed increase opens the possibility of building large hydrogen production facilities, for example in the Sahara where sunshine is plentiful. Or we may be able to achieve far more efficient conversion of solar energy into electricity,” Sun says.

“I’m convinced that, within ten years, this type of research will lead to technology that’s inexpensive enough to compete with coal,” he continues. “It’s no surprise that [U.S. President] Barack Obama is investing billions of dollars in this area.”

With some 20 years researching oxidation catalysts — including 10 years at KTH — Sun says he and many other scholars are convinced that this is the avenue to pursue for alternatives to fossil fuels. “Solar is the best hope for renewable energy,” he says.

Professor Sun’s research group, which includes scientists at Uppsala University and Stockholm University, has received research funding from the Knut and Alice Wallenberg Foundation and the Swedish Energy Agency. KTH Professor Lars Kloo and Professor Sun are also involved in a joint research centre with Dalian University of Technology (DUT) in China.

By Peter Larsson. Edited by Kevin Billinghurst