Extracting clean fuel from sunlight

Extracting clean fuel from sunlight
The experimental photoelectrosynthetic cell described in the new study. Technologies of this kind combine light-gathering semiconductors and catalytic materials capable of chemical reactions that produce clean fuel. Credit: Biodesign Institute at Arizona State University

Securing enough energy to meet human needs is one of the greatest challenges society has ever faced. Previously reliable sources—oil, gas and coal—are degrading air quality, devastating land and ocean and altering the fragile balance of the global climate, through the release of CO2 and other greenhouse gases. Meanwhile, earth's rapidly industrializing population is projected to reach 10 billion by 2050. Clean alternatives are a matter of urgent necessity.

Researchers at ASU's Biodesign Center for Applied Structural Discovery are exploring new technologies that could pave the way to clean, to help meet daunting global demand.

In new research appearing in the Journal of the American Chemical Society (JACS), the flagship journal of the ACS, lead author Brian Wadsworth, along with colleagues Anna Beiler, Diana Khusnutdinova, Edgar Reyes Cruz, and corresponding author Gary Moore describe technologies that combine light-gathering semiconductors and catalytic materials capable of that produce .

The new study explores the subtle interplay of the primary components of such devices and outlines a theoretical framework for understanding the underlying fuel-forming reactions. The results suggest strategies for improving the efficiency and performance of such hybrid technologies, bringing them a step closer to commercial viability.

The production of hydrogen and reduced forms of carbon by these technologies could one day supplant fossil fuel sources for a broad range of reduced carbon commodities, including fuels, plastics and .

"In this particular work we've been developing systems that integrate light capture and conversion technologies with chemical-based storage strategies," says Moore, who is an assistant professor in ASU's School of Molecular Sciences. Rather than direct generation of electricity from sunlight, this new breed of technology uses solar energy to drive chemical reactions capable of producing fuels, which store the sun's energy in chemical bonds. "That's where catalysis becomes extremely important. It's the chemistry of controlling both the selectivity of reactions and the overall energy requirements for driving those transformations," Moore says.

Something new under the sun

One of the most attractive sources for sustainable, carbon-neutral energy production is both ancient and abundant: sunlight. Indeed, adoption of technologies has gained significant momentum in recent years.

Photovoltaic (PV) devices, or solar cells, gather sunlight and transform the energy directly into electricity. Improved materials and lowered costs have made photovoltaics an attractive energy option, particularly in sun-drenched states like Arizona, with large solar arrays covering multiple acres capable of powering thousands of homes.

"But just having access to solar power using photovoltaics is not enough," Moore notes. Many renewables like sunlight and wind power are not always available, so storage of intermittent sources is a key part of any future technology to meet global human energy demands on a large scale.

As Moore explains, borrowing a page from Nature's handbook may help researchers harness the sun's radiant energy to generate sustainable fuels. "One thing is clear," Moore says. "We are likely to continue using fuels as part of our energy infrastructure for the foreseeable future, especially for applications involving ground and air transportation. That's where the bioinspired part of our research becomes particularly relevant—looking to Nature for hints as to how we might develop new technologies for producing fuels that are carbon free or neutral."

Solar flair

One of Nature's more impressive tricks involves the use of sunlight to produce energy-rich chemicals, a process mastered billions of years ago by plants and other photosynthetic organisms. "In this process, light is absorbed, and the energy is used to drive a series of complex biochemical transformations that ultimately produce the foods we eat and, over long geological time scales, the fuels that run our modern society," Moore says.

In the current study, the group analyzed key variables governing the efficiency of chemical reactions used to produce fuel through various artificial devices. "In this paper, we've developed a kinetic model to describe the interplay between light absorption at the semiconductor surface, charge migration within the semiconductor, charge transfer to our catalyst layer and then the chemical catalysis step," said Wadsworth.

The model the group developed is based on a similar framework governing enzyme behavior, known as Michaelis-Menten kinetics, which describes the relationship between enzymatic reaction rates and the medium in which the reaction takes place (or substrate). Here, this model is applied to technological devices combining light-harvesting semiconductors and for fuel formation.

"We describe the fuel-forming activities of these hybrid materials as a function of light intensity and also the potential," Wadsworth says. (Similar Michaelis-Menten-type kinetic models have proven useful in analyzing such phenomena as antigen-antibody binding, DNA-DNA hybridization, and protein-protein interaction.)

In modeling the dynamics of the system, the group made a surprising discovery. "In this particular system we are not limited by how fast the catalyst can drive the chemical reaction," Moore says. "We're limited by the ability to deliver electrons to that catalyst and activate it. That is related to the light intensity striking the surface. Brian, Anna, Diana, and Edgar have shown in their experiments that increasing the light intensity increases the rate of fuel formation."

The discovery has implications for the future design of such devices with an eye toward maximizing their efficiencies. "Simply adding more catalyst to the surface of the hybrid material does not result in greater rates of fuel production. We need to consider the light absorbing properties of the underpinning semiconductor, which in turn forces us think more about the selection of the catalyst and how the catalyst interfaces with the light absorbing component."

Ray of hope

Much work remains to be done before such solar-to-fuels solutions are ready for prime time. Making technologies like these practical for human demands requires efficiency, affordability and stability. "Biological assemblies have the ability to self-repair and reproduce; technological assemblies have been limited in this aspect. It's one area where we can learn more from biology," Moore says.

The task could hardly be more urgent. Global demand for energy is projected to swell from around 17 terawatts today to a staggering 30 terawatts by mid-century. In addition to significant scientific and technological hurdles, Moore stresses that profound policy changes will also be essential. "There's a real question of how we're going to meet our future energy demands. If we're going to do it in an environmentally conscious and egalitarian manner, it's going to take a serious political commitment."

The new research is a step on the long pathway to a sustainable future. The group notes that their findings are important because they are likely relevant to a wide range of chemical transformations involving light-absorbing materials and catalysts. "The key principles, particularly the interplay between illumination intensity, light absorption and catalysis should apply to other materials as well," Moore says.


Explore further

ASU research graces cover of ACS journal

More information: Brian L. Wadsworth et al, The Interplay Between Light Flux, Quantum Efficiency, and Turnover Frequency in Molecular-modified Photoelectrosynthetic Assemblies, Journal of the American Chemical Society (2019). DOI: 10.1021/jacs.9b07295
Citation: Extracting clean fuel from sunlight (2019, September 3) retrieved 17 September 2019 from https://phys.org/news/2019-09-fuel-sunlight.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Sep 03, 2019
"We describe the fuel-forming activities of these hybrid materials as a function of light intensity and also the potential," Wadsworth says. (Similar Michaelis-Menten-type kinetic models have proven useful in analyzing such phenomena as antigen-antibody binding, DNA-DNA hybridization, and protein-protein interaction.)

In modeling the dynamics of the system, the group made a surprising discovery. "In this particular system we are not limited by how fast the catalyst can drive the chemical reaction," Moore says. "We're limited by the ability to deliver electrons to that catalyst and activate it."


Now THIS is what I would call a 'worthwhile commitment'. But I would like to know if the resulting fuel will be a gas or a liquid, or a stream of Electrons piped into a vehicle engine. And what kind of engine would that be.
Other civilisations elsewhere are capable of drawing energy from their Star directly by specially constructed ships that have a length of tubing to suck energy.

Sep 03, 2019
Clean Energy

Spin a coil in a magnetic field propels electrons through this coil
So far
No adverse environmental affects hath been produced
For these are simply
Moving a copper wires
Through a magnetic field
Lenz law

The next stage
Is a propulsive force
That propels these copper wires through this magnetic field
With no adverse environmental affects

p.s. for Extracting clean fuel from sunlight requires the use of catalysts, as this is this slippery slope of environmentally unfriendly metals and dirty production methods that destroys this very ethos!

Sep 03, 2019
or a stream of Electrons piped into a vehicle engine. And what kind of engine would that be
Pussytard thinks electrons are combustible.

Of course she does.

Sep 03, 2019
Otto, YOUR MOTHER AND HER MOTHER ARE PUSSYTARDS. You keep forgetting this.
And HOW EXACTLY do you KNOW what they can and can't do, Otto? I never said anything about 'COMBUSTIBLE'. IT'S ALL IN YOUR LOONEYTICK IMAGINATION, OTTO.

I SUGGEST THAT YOU READ MY COMMENT AGAIN - TWICE, otto. And stop following me around in all the phorums. We all know that you're gay, but I don't have what you THINK I have.

Sep 04, 2019
p.s. for Extracting clean fuel from sunlight requires the use of catalysts, as this is this slippery slope of environmentally unfriendly metals and dirty production methods that destroys this very ethos!

I've taken courses on environmental & green chemistry and they all promote the use of catalysts. They don't react, are reusable and make things a lot faster and easier. Can you point out the reasons why you criticize them so much?

Sep 04, 2019
Catalysis

is the process
of increasing the rate
of a chemical reaction
by adding a substance
known as a Catalyst

which is not consumed
in the Catalyzed reaction
continually acting repeatedly

Because of this
only very small amounts
of Catalyst are required
to alter the reaction rate

chemical reactions
occur faster
in the presence of a Catalyst
because the Catalyst provides
an alternative reaction pathway
with a lower activation energy

p.s. cortezz, nothing in this world comes with a freebie ticket, so the search is on as to this particular catalyst and how its manufactured, as this article is talking computer modelling, if everything came with a freebie ticket, these atoms would fall apart

Sep 04, 2019
For what is difficult to believe: A Catalyst, repeating without end

A Catalyst
is a substance
which is not consumed
in the Catalyzed reaction
continually acting repeatedly

Because cortezz
acting repeatedly
without end
has this same ethos
as perpetual motion

for this means
it is possible
to find a Catalyst
involved in the combustion process
in the cylinders of piston engines
so that only water is emitted from this exhaust pipe

Sep 04, 2019
So you are combining catalysts and environmentally unfriendly metals and dirty production methods just because? No science or facts behind it?

Sep 04, 2019
PLEASE NOTE: Surveillance_Egg_Unit and TheGhostofOtto1923

THIS A PUBLIC SITE
where there
are no restrictions
Barring Age Related Readers!


Sep 04, 2019
Clean Emissions in Existing Technology
cortezz> So you are combining catalysts and environmentally unfriendly metals and dirty production methods just because? No science or facts behind it?

At Staffordshire University
it was suggested
that
using a nano magnetic filter
in the air filter of combustion engines
due to nitrogen and oxygen
behaving oppositely in a powerful magnetic field
it is possible to separate oxygen from nitrogen
there by, feeding only oxygen and petrol in the cylinders
Producing more power per lb of fuel, and only water from the exhaust pipe

p.s. and cortezz, not a catalyst in sight, not even a catalytic exhaust pipe

Sep 04, 2019
Clean Emissions in Existing Technology

At Staffordshire University
it was suggested
that
using a nano magnetic filter
in the air filter of combustion engines
due to nitrogen and oxygen
behaving oppositely in a powerful magnetic field
it is possible to separate oxygen from nitrogen
there by, feeding only oxygen and petrol in the cylinders
Producing more power per lb of fuel, and only water from the exhaust pipe

p.s. and cortezz, not a catalyst in sight, not even a catalytic exhaust pipe

Sure, there are options besides catalysts but this article is not about petrol engines, it's about creating fuel with sunlight.

I just find it strange that you're attacking catalysts, which are quite popular among the general consensus, in a random article without even bringing up any evidence.

Sep 04, 2019
For this is what this article is suggesting: The Energy of Sunlight

Using the energy of Sunlight
with the assistance of Catalysts
break down emissions into their component parts
without degrading the Catalyst

for CO2 or H2O released as emissions
Sunlight can break apart CO2 and H2O
because the energy to do so, comes from an unlimited source, our Sun

for there is an important point
if CO2 or H2O are broken apart
the life giving Oxygen can be returned to our atmosphere
or
we can, like these Catalyzed reactions, continually acting repeatedly, without end

we can repeatedly break apart our emissions
using the energy in our Sun sunlight
To burn yet again in our piston engines, a repeatedly repeating action!

p.s. because the intention in this article, is to use sunlight, to provide the energy, currently in use

Sep 04, 2019
If these Catalysts are as good as they seem
cortezz> I just find it strange that you're attacking catalysts, which are quite popular among the general consensus, in a random article without even bringing up any evidence.

You can see, I've got some pretty nifty uses, for these Catalysts!

Sep 04, 2019
If you can use Sunlight and Catalysts

One intention is to pass hydrogen into a nano-matrix
where it is stored in your petrol tank instead of petrol
where it combines with oxygen
producing water
where
with the use of replaceable Catalysts
pass this water back in the matrix
where it is broken apart
into its component parts
where it combines with oxygen
producing water

for the energy to break these molecules apart
comes from the replaceable Catalyst
which you buy at existing petrol stations
instead of buying petrol
where the actual fuel is water

so you have two tanks
one of water
and one a matrix
of
Hydrogen and Catalysts

Sep 04, 2019
Now I little understand what you mean. Nevertheless, I think it's all good if we can invent a carbon neutral power source.

BTW, I'm little suspicious about your claim of the nano magnetic filter petrol engine. It's magically producing only H2O as exhaust even thought it is also fed with carbon. I'm a master of science but this is over my head.

Sep 04, 2019
Magically producing only H2O
cortezz> BTW, I'm little suspicious about your claim of the nano magnetic filter petrol engine. It's magically producing only H2O as exhaust even thought it is also fed with carbon. I'm a master of science but this is over my head.

Its ages since the chemistry professor at Stafford Uni discussed this
Your right, he said only CO2, water was a slip of the pen
He did not dismiss the nano magnetic filter
as he was discussing paramagnetic oxygen
No nitrous oxides, only carbon dioxide to worry about

Sep 04, 2019
nothing in this world comes with a freebie ticket
Nonsense, how much was your bill for all the sunlight you received last month? How much did you have to pay for all the oxygen you consumed? How much did the tree charge you for its labor in producing the apple you enjoyed? What exactly was your price of admission for this fun ride through the cosmos?

Just because you pay money to a group of shysters every month doesn't mean it's the only game in the universe -- in light of science and the truth, it basically just means you're a sucker for believing a bunch of shysters...

Sep 04, 2019
Well, certainly there must be some catalyst that would increase the solar breakdown rate of CO2...?

Sep 04, 2019
One should note that these forms of synfuel/power-2-gas/power-2-fuel or however you want to call them never work with ambient CO2. They always work with industrially produced, highly concentrated CO2.
So calling this "carbon neutral" is sort of a joke. It's more of a technology that would let CO2 intensive industries survive a little longer because "hey, look: our waste products can be used again as fuel...and THEN dumped into the atmosphere...so WE aren't the polluters. Aren't we great/green?")

Sep 05, 2019
Nothing in this World comes with a Freebie Ticket

There are Two Points of Interest
1, a catalyst increases the rate of reaction
2, a catalyst lowers the activation energy

1a, Fore if you're breaking H2O apart
With sunlight by increasing the activation rate
The reaction still requires the same energy
But in a shorter time

2a, By lowering the activation energy
Is increasing the rate of reaction
Because the reaction occurs sooner
The reaction still requires the same energy
But in a shorter time

The Morel of this Perpetual Motion
The Energy to Form a Bond is the Energy to Break a Bond

For it always requires more energy to break the bond
Than you get in return
Nothing in this World comes with a Freebie Ticket

p.s. which is why, solar fusion is so massive, the sun is losing more energy that it requires to maintain fusion, its mass is acting as an insulation blanket

Sep 05, 2019
2a, By lowering the activation energy
Is increasing the rate of reaction
Because the reaction occurs sooner
The reaction still requires the same energy
But in a shorter time

What is this nonsense once again: A catalyst lowers the activation energy but the reaction still requires the same energy. What???

What I've been taught is that a catalyst provides an alternative route with lower activation energy to the end product. It usually makes the reaction both faster and to happen in lower energies.

Even wikipedia agrees: A catalyst increases the rate of reaction without being consumed in the reaction. In addition, the catalyst lowers the activation energy, but it does not change the energies of the original reactants or products, and so does not change equilibrium

Sep 05, 2019
Nothing in this World comes with a Freebie Ticket

There are Two Points of Interest
1, a catalyst increases the rate of reaction
2, a catalyst lowers the activation energy
...
The Morel of this Perpetual Motion
The Energy to Form a Bond is the Energy to Break a Bond

For it always requires more energy to break the bond
Than you get in return
Nothing in this World comes with a Freebie Ticket

p.s. which is why, solar fusion is so massive, the sun is losing more energy that it requires to maintain fusion, its mass is acting as an insulation blanket

Well, yeah...
Which is why stars have defined lifetimes...

Sep 05, 2019
Well, certainly there must be some catalyst that would increase the solar breakdown rate of CO2...?
Yeah. Electrons. Ask pussytard.
What is this nonsense once again: A catalyst lowers the activation energy but the reaction still requires the same energy. What???
Its called poetic license. They can e'en invent their own words.

Sep 05, 2019
Firstly, cortezz
cortezz> What I've been taught is that a catalyst provides an alternative route with lower activation energy to the end product. It usually makes the reaction both faster and to happen in lower energies.

You didn't answer your own question
I've found, it's fatal to say "What I've been taught is"
Fore
What
You
Have been taught, might be, for what we're about to receive
As in
With lower activation energy
Makes the reaction both faster
To happen in lower energies

For cortezz, this vital bit "to happen in lower energies"
Is "happen in lower energies"
At both side of the equation which equals no gain
Or is starting at a lower energy and ending at its normal energy, which equals a gain?

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