November 11 () –
Chemists from the University of Chicago have presented an innovative system for artificial photosynthesis that is more productive than previous artificial systems by an order of magnitude.
Unlike regular photosynthesis, which produces carbohydrates from carbon dioxide and water, artificial photosynthesis could produce ethanol, methane or other fuels.
Although it has a long way to go before it can become a way to power vehicles, the authors claim that their method –featured in Nature Catalysis– it gives scientists a new direction to explore, and may be useful in the short term for the production of other chemicals.
“This is a vast improvement over existing systems, but just as importantly, we were able to establish a very clear understanding of how this artificial system works at the molecular level, something that had not been achieved before“, said it’s a statement Wenbin Lin, professor of chemistry at the University of Chicago and lead author of the study.
“Without natural photosynthesis, we wouldn’t be here. It made the oxygen we breathe on Earth and produces the food we eat,” Lin said. “But it’s never going to be efficient enough to supply us with fuel to drive cars, so we’re going to need something else.”
The problem is that photosynthesis is designed to create carbohydrates, which are great for fueling us, but not our cars, which need much more concentrated energy. Therefore, researchers seeking to create alternatives to fossil fuels they must redesign the process to create more energy-dense fuels, such as ethanol or methane.
In nature, photosynthesis is carried out by various highly complex assemblies of proteins and pigments. They absorb water and carbon dioxide, break molecules apart, and rearrange atoms to produce carbohydrates, a long chain of compounds of hydrogen, oxygen, and carbon. The scientists, however, need to rework the reactions to produce a different arrangement with just hydrogen surrounding a juicy carbon core: CH4, also known as methane.
This reengineering is much more complicated than it seems; people have been tinkering with it for decades, trying to get close to nature’s efficiency.
Lin and his lab team thought they might try adding something that artificial photosynthesis systems to date haven’t included: 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 linking organic molecules. They then designed the MOFs as a single layer, in order to provide the maximum surface area for chemical reactions, and immersed everything in a solution that included a cobalt compound to transport electrons. Finally, they added amino acids to the MOFs and experimented to find out which worked best.
They were able to make improvements to both halves of the reaction: the process that breaks down water and the one that adds electrons and protons to carbon dioxide. In both cases, the amino acids helped make the reaction more efficient.
MANY ORDERS OF MAGNITUDE MUST BE INCREASED
However, even with the significantly improved performance, artificial photosynthesis has a long way to go before it can produce enough fuel to be relevant for widespread use. “Where are we now, it would need to increase by many orders of magnitude to produce a sufficient amount of methane for our consumptionLin said.
The breakthrough could be broadly applied to other chemical reactions as well; a lot of fuel needs to be produced for it to have an impact, but much smaller amounts of some molecules, like the starting materials for making drugs and nylon, among others, could be very useful.
