Madrid. Cambridge scientists have developed an efficient concept for converting carbon dioxide into clean, sustainable fuels, without unwanted by-products or waste.
It had already been shown that biological catalysts or enzymes can cleanly produce fuels using renewable energy sources, albeit with low efficiency.
Recent research improved fuel production effectiveness 18 times in a laboratory, showing that polluting carbon emissions can be successfully transformed into green fuels without wasting energy. The results are reported in two articles in Nature Chemistry and Proceedings of the National Academy of Sciences.
Most methods also produce unwanted by-products, such as hydrogen. Scientists can alter the chemical conditions to minimize CO₂ production, but it also lowers the CO₂ conversion yield, so a cleaner fuel can be produced, albeit at the cost of efficiency.
The proof of concept developed by Cambridge relies on enzymes isolated from bacteria to drive chemical reactions that convert CO₂ into fuel, a process called electrolysis.
Enzymes are more efficient than other catalysts, such as gold, but are very sensitive to their local chemical environment. If this is not exactly the right one, they fall apart and the chemical reactions are slow.
In collaboration with a team from the Universidade Nova de Lisboa, the specialists developed a method to improve the efficiency of the electrolysis by adjusting the conditions of the solution in order to alter the local environment of the enzymes.
“These have evolved over millions of years to be extremely efficient and selective, and are excellent for fuel production because there are no unwanted by-products,” explained Esther Edwardes Moore of Cambridge, first author of the paper.
“However, enzyme sensitivity poses a different set of challenges. Our method takes this quality into account, so that the local environment is adjusted to match the enzyme’s ideal working conditions.”
To further improve the local environment, the specialists showed how two enzymes can work together, one producing fuel and the other controlling the environment. They found that adding another enzyme speeded up the reactions, increasing efficiency and reducing unwanted by-products.
The researchers say that the secret to more efficient CO2 electrolysis lies in the catalysts. There have been great improvements in the development of the synthetic type in recent years, but they still do not reach that of the enzymes used in this work.
“Once you manage to make better catalysts, a lot of the problems with CO₂ electrolysis just go away,” said Sam Cobb, another author. We are showing the scientific community that once we can produce the catalysts of the future we will be able to eliminate many of today’s trade-offs, as what we learn from enzymes can be transferred to synthetic catalysts.”
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