New, nature-inspired concepts for turning CO2 into clean fuels

Date:
February 28, 2022
Source:
University of Cambridge
Summary:
Researchers have developed an efficient concept to turn carbon
dioxide into clean, sustainable fuels, without any unwanted
by-products or waste.



FULL STORY ========================================================================== Researchers have developed an efficient concept to turn carbon dioxide
into clean, sustainable fuels, without any unwanted by-products or waste.


==========================================================================
The researchers, from the University of Cambridge, have previously shown
that biological catalysts, or enzymes, can produce fuels cleanly using renewable energy sources, but at low efficiency.

Their latest research has improved fuel production efficiency by 18
times in a laboratory setting, demonstrating that polluting carbon
emissions can be turned into green fuels efficiently without any wasted
energy. The results are reported in two related papers in Nature Chemistry
and Proceedings of the National Academy of Sciences.

Most methods for converting CO2 into fuel also produce unwanted
by-products such as hydrogen. Scientists can alter the chemical conditions
to minimise hydrogen production, but this also reduces the performance
for CO2 conversion: so cleaner fuel can be produced, but at the cost
of efficiency.

The Cambridge-developed proof of concept relies on enzymes isolated from bacteria to power the chemical reactions which convert CO2 into fuel,
a process called electrolysis. Enzymes are more efficient than other
catalysts, such as gold, but they are highly sensitive to their local
chemical environment. If the local environment isn't exactly right,
the enzymes fall apart and the chemical reactions are slow.

The Cambridge researchers, working with a team from the Universidade
Nova de Lisboa in Portugal, have developed a method to improve the
efficiency of electrolysis by fine-tuning the solution conditions to
alter the local environment of the enzymes.



========================================================================== "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," said Dr Esther Edwardes Moore from Cambridge's Yusuf Hamied Department of Chemistry, first author of the
PNAS paper. "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."
The researchers used computational methods to design a system to improve
the electrolysis of CO2. Using the enzyme-based system, the level of
fuel production increased by 18 times compared to the current benchmark solution.

To improve the local environment further, the team showed how two
enzymes can work together, one producing fuel and the other controlling
the environment.

They found that by adding another enzyme, it sped up the reactions,
both increasing efficiency and reducing unwanted 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 the Nature Chemistry paper. "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." "Electrolysis has a big part
to play in reducing carbon emissions," said Professor Erwin Reisner,
who led the research. "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."
The researchers say that the secret to more efficient CO2 electrolysis
lies in the catalysts. There have been big improvements in the development
of synthetic catalysts in recent years, but they still fall short of
the enzymes used in this work.



========================================================================== "Once you manage to make better catalysts, many of the problems with CO2 electrolysis just disappear," said 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." "Once
we designed the concept, the improvement in performance was startling,"
said Edwardes Moore. "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."
"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," said Cobb.

Erwin Reisner is a Fellow of St John's College, Cambridge. Sam Cobb is
a Research Fellow of Darwin College, Cambridge. Esther Edwardes Moore
completed her PhD with Corpus Christi College, Cambridge. The research
was supported in part by the European Research Council, the Leverhulme
Trust, and the Engineering and Physical Sciences Research Council.

========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
text of this story is licensed under a Creative_Commons_License. Note:
Content may be edited for style and length.


========================================================================== Journal References:
1. Esther Edwardes Moore, Samuel J. Cobb, Ana Margarida Coito, Ana Rita
Oliveira, Ine^s A. C. Pereira, Erwin Reisner. Understanding the
local chemical environment of bioelectrocatalysis. Proceedings of
the National Academy of Sciences, 2022; 119 (4): e2114097119 DOI:
10.1073/ pnas.2114097119
2. Cobb, S.J., Badiani, V.M., Dharani, A.M. et al. Fast CO2 hydration
kinetics impair heterogeneous but improve enzymatic CO2 reduction
catalysis. Nat. Chem., 2022 DOI: 10.1038/s41557-021-00880-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220228114338.htm

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