Scientists are homing in on a recipe that would enable the future production of entirely renewable, clean energy from which water would be the only waste product.
From:
Trinity College Dublin
July 7, 2021 -- Using their expertise in
chemistry, theoretical physics and artificial intelligence, the team is now
fine-tuning the recipe with the genuine belief that the seemingly impossible
will one day be reality.
Using their expertise in chemistry,
theoretical physics and artificial intelligence, the team is now fine-tuning
the recipe with the genuine belief that the seemingly impossible will one day
be reality.
Initial work in this area, reported just
under two years ago, yielded promise. That promise has now been amplified
significantly in the exciting work just published in leading journal, Cell
Reports Physical Science.
Energy for a song -- the theory, and the
problem
Reducing humanity's carbon dioxide (CO2)
emissions is arguably the greatest challenge facing 21stcentury civilisation --
especially given the increasing global population and the heightened energy
demands that come with it.
One beacon of hope is the idea that we
could use renewable electricity to split water (H2O) to produce
green, energy-rich hydrogen (H2), which could then be stored and
used in fuel cells. This is an especially interesting prospect in a situation
where wind and solar energy sources produce electricity to split water, as this
would allow us to store energy for use when those renewable sources are not
available.
The essential problem, however, is that
water is very stable and requires a great deal of energy to break up; there is
no point using much more energy than you get back from such an effort. A
particularly major hurdle to clear is this "overpotential" associated
with the production of oxygen, which is the bottleneck reaction in splitting
water to produce H2.
Although certain elements are effective
at splitting water, such as Ruthenium or Iridium, these are prohibitively
expensive and scarce for global commercialisation. Other, cheaper options tend
to suffer in terms of their efficiency and/or their robustness. In fact, at
present, nobody has discovered catalysts that are cost-effective and robust for
significant periods of time.
So, how do you solve such a riddle? Stop
before you imagine lab coats, glasses, beakers and funny smells; this work was
done entirely through a computer.
By bringing together chemists and
theoretical physicists, the Trinity team behind the latest breakthrough
combined chemistry smarts with very powerful computers to find one of the
"holy grails" of catalysis.
What did the team find?
Then: Two years ago, the team discovered
that science had been underestimating the activity of some of the more reactive
catalysts and, as a result, the dreaded "overpotential" hurdle seemed
easier to clear. Furthermore, in refining a long-accepted theoretical model
used to predict the efficiency of water splitting catalysts, they made it far
easier to search for the elusive "green bullet" catalyst.
Now: Their subsequent searches, made
using an automated combinatorial approach and advanced quantum chemical
modelling, have pinpointed nine earth-abundant combinations of metals and
ligands (which glue them together to generate the catalysts) as highly
promising leads for experimental investigation.
Three metals stand out (chromium,
manganese, iron) for the team as being especially promising. Thousands of
catalysts based around these key components can now be placed in a melting pot
and assessed for their abilities as the hunt for the magic combination
continues.
Max García-Melchor, Ussher Assistant
Professor in Chemistry at Trinity, is the senior author on the landmark
research. He said:
"Two years ago, our work had made
the hunt for the holy grail of catalysts seem a little more manageable. Now, we
have taken another major leap forward by narrowing the search area
significantly and speeding up the way we search.
"Until recently we were looking for
a tiny needle in a huge haystack. After reducing the size of the haystack, we
have now hoovered up plenty of the remaining hay. To put a sense of scale on
this, two years ago we had screened 17 catalysts. Now we have screened 444 and
believe it won't be long before we have a database with 80,000 'screenable'
catalysts in it.
"'How can we live sustainably?'
That is arguably the biggest and most pressing question facing 21st century
society. I believe researchers from all disciplines can help to answer that,
and we feel a particular strength of our pursuit is the multi-disciplinary
approach we are taking."
Michael Craig, PhD Candidate at Trinity,
is the first author of the journal article. He added:
"It seems hopeful that science
could provide the world with entirely renewable energy, and this latest work
provides a theoretical basis to optimise sustainable ways to store this energy
and goes beyond that by pinpointing specific metals that offer the greatest
promise.
"A lot of research has focused on
the effective yet prohibitively expensive metals as possible candidates, even
though these are far too rare to do the heavy lifting required to store enough
hydrogen for society. We are focused on finding a long-term, viable option. And
we hope we will."
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