CO2 converted into clean, sustainable fuel by University of Cambridge researchers
An efficient way to turn carbon dioxide into clean, sustainable fuels without unwanted by-products or waste has been developed by University of Cambridge researchers.
It follows their earlier work showing how enzymes - biological catalysts - can produce fuels cleanly using renewable energy sources, but at low efficiency.
In the new research, they have improved fuel production efficiency by 18 times in a laboratory setting.
Most methods of converting C02 into fuel produce unwanted by-products such as hydrogen. While this can be minimised, the performance for C02 conversion is compromised.
The Cambridge proof of concept deploys enzymes isolated from bacteria to power the conversion reactions in the process of electrolysis.
Enzymes are more efficient than catalysts such as gold but their chemical environment must be exactly right, or the reactions are slow.
Working with a team at Universidade Nova de Lisboa in Portugal, the team improved the efficiency of electrolysis by fine-tuning the solution conditions.
Dr Esther Edwardes Moore, from Cambridge’s Yusuf Hamied Department of Chemistry, author of a paper published in PNAS on the work, said: “Enzymes have evolved over millions of years to be extremely efficient and selective, and they’re great for fuel-production because there aren’t any unwanted by-products.
“However, enzyme sensitivity throws up a different set of challenges. Our method accounts for this sensitivity, so that the local environment is adjusted to match the enzyme’s ideal working conditions.”
Computational methods were used to design the more efficient system and the team also showed how two enzymes can work together, with one producing fuel and the other controlling the environment. Adding another enzyme sped up the reactions, increasing efficiency and reducing by-products.
“We ended up with just the fuel we wanted, with no side-products and only marginal energy losses, producing clean fuels at maximum efficiency,” said Dr Sam Cobb, first author of a Nature Chemistry paper on the work. “By taking our inspiration from biology, it will help us develop better synthetic catalyst systems, which is what we’ll need if we’re going to deploy CO2 electrolysis at a large scale.”
St John’s fellow Professor Erwin Reisner, who led the research, added: “Electrolysis has a big part to play in reducing carbon emissions. Instead of capturing and storing CO2, which is incredibly energy-intensive, we have demonstrated a new concept to capture carbon and make something useful from it in an energy-efficient way.”
Synthetic catalysts have been developed in recent years, but fall short of the enzymes used in this research.
“Once you manage to make better catalysts, many of the problems with CO2 electrolysis just disappear,” said Dr Cobb. “We’re showing the scientific community that once we can produce catalysts of the future, we’ll be able to do away with many of the compromises currently being made, since what we learn from enzymes can be transferred to synthetic catalysts.”
Dr Edwardes Moore, who completed her PhD at Corpus Christi College, added: “Once we designed the concept, the improvement in performance was startling. I was worried we’d spend years trying to understand what was going on at the molecular level, but once we truly appreciated the influence of the local environment, it evolved really quickly.”
Darwin College research fellow Dr Cobb concluded: “In future we want to use what we have learned to tackle some challenging problems that the current state-of-the-art catalysts struggle with, such as using CO2 straight from air as these are conditions where the properties of enzymes as ideal catalysts can really shine.”
The research was supported in part by the European Research Council, the Leverhulme Trust and the Engineering and Physical Sciences Research Council.
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