Chemists create an ‘artificial photosynthesis’ system ten times more efficient than existing systems

For the past two centuries, people have relied on fossil fuels for concentrated energy; hundreds of millions of years of photosynthesis packed into a convenient, energy-rich substance. But that supply is finite and the consumption of fossil fuels has a huge negative impact on the Earth’s climate.

“The biggest challenge that many people don’t realize is that even nature has no solution for the amount of energy we use,” said University of Chicago chemist Wenbin Lin. Not even photosynthesis is that okay, he said, “We’re going to have to do better than nature, and that’s scary.”

One possible option that scientists are investigating is “artificial photosynthesis“—reworking a factory’s system to make our own types of fuels. However, the chemical equipment in a single sheet is incredibly complex and not so easy to use for our own purposes.

A Nature Catalysis study by six chemists from the University of Chicago shows an innovative new system for artificial photosynthesis that is an order of magnitude more productive than previous artificial systems. Unlike ordinary photosynthesis, which produces carbohydrates from carbon dioxide and water, artificial photosynthesis can produce ethanol, methane or other fuels.

While there’s still a long way to go before it can become a way for you to fuel your car every day, the method gives scientists a new direction to explore – and could be useful in the shorter term for the production of others. chemicals.

“This is a huge improvement over existing systems, but just as importantly, we were able to provide a very clear understanding of how this artificial system works on the molecular levelwhich has not been achieved before,” said Lin, James Franck Professor of Chemistry at the University of Chicago and senior author of the study.

‘We need something else’

“We wouldn’t be here without natural photosynthesis. It made the oxygen we breathe on Earth and it makes the food we eat,” Lin said. “But it will never be efficient enough to fuel us to drive cars, so we will need something else.”

The problem is that photosynthesis is built to create carbohydrates, which are great for fueling us, but not for our cars, which require much more concentrated energy. So researchers who want to create alternatives to fossil fuels need to redesign the process to create more energy-rich fuels, such as ethanol or methane.

In nature, photosynthesis is carried out by various highly complex compositions of proteins and pigments. They take in water and carbon dioxide, break the molecules apart and rearrange the atoms to make carbohydrates — a long series of hydrogen-oxygen-carbon bonds. However, scientists must rework the reactions to instead produce a different arrangement using only hydrogen around a juicy carbon core – CH₄also called methane.

This re-engineering is much trickier than it sounds; humans have been tinkering with it for decades to get closer to nature’s efficiency.

Lin and his lab team thought they could try adding something that artificial photosynthesis systems don’t include until now: amino acids.

The team started with a type of material called a metal-organic framework or MOF, a class of compounds made up of: metal ions held together by organic linking molecules. They then designed the MOFs as a single layer, to provide the maximum surface area for chemical reactions, and immersed everything in a solution containing a cobalt compound to transport electrons around. Finally, they added amino acids to the MOFs and experimented to find out which one worked best.

They were able to make improvements in both halves of the reaction: the process that breaks down water and the process that adds electrons and protons to carbon dioxide. In both cases, the amino acids helped the reaction run more efficiently.

However, even with its significantly improved performance, artificial photosynthesis still has a long way to go before it can produce enough fuel to be relevant for widespread use. “Where we are now, it would have to scale up by many orders of magnitude to make enough methane for our consumption,” Lin said.

The breakthrough can also be widely applied to other chemical reactions; you have to make a lot of fuel to have an effect, but much smaller amounts of some molecules, such as the starting materials to make pharmaceuticals and nylons, among other things, can be very useful.

“So many of these fundamental processes are the same,” Lin says. “If you develop good chemistry, they can be connected to many systems.”