Carbon
spheres — microscope images. A fast, green and one-step method for producing
porous carbon spheres, which are a vital component for carbon capture
technology and for new ways of storing renewable energy, has been developed by
Swansea University researchers. Carbon spheres range in size from nanometers to
micrometers. storage and conversion, catalysis, gas adsorption and storage,
drug and enzyme delivery, and water treatment. Credit: ESRI, Swansea University
A fast,
green and one-step method for producing porous carbon spheres, which are a vital
component for carbon capture technology and for new ways of storing renewable
energy, has been developed by Swansea University researchers.
The method
produces spheres that have good capacity for carbon capture, and it works
effectively at a large scale.
Carbon
spheres range in size from nanometers to micrometers. Over the past decade they
have begun to play an important role in areas such as energy storage and
conversion, catalysis, gas adsorption and storage, drug and enzyme delivery,
and water treatment.
They are
also at the heart of carbon capture technology, which locks up carbon rather
than emitting it into the atmosphere, thereby helping to tackle climate change.
The
problem is that existing methods of making carbon spheres have drawbacks. They
can be expensive or impractical, or they produce spheres that perform poorly in
capturing carbon. Some use biomass, making them more environmentally friendly,
but they require a chemical to activate them.
This is
where the work of the Swansea team, based in the University’s Energy Safety
Research Institute, represents a major advance. It points the way towards a
better, cleaner and greener way of producing carbon spheres.
The team
adapted an existing method known as CVD — chemical vapor deposition. This
involves using heat to apply a coating to a material. Using pyromellitic acid
as both carbon and oxygen source, they applied the CVD method at different
temperatures, from 600-900 °C. They then studied how efficiently the spheres
were capturing CO2 at different pressures and temperatures
They found
that:
800 °C was
the optimum temperature for forming carbon spheres
The
ultramicropores in the spheres that were produced gave them a high carbon
capture capacity at both atmospheric and lower pressures
Specific
surface area and total pore volume were influenced by the deposition
temperature, leading to an appreciable change in overall carbon dioxide capture
capacity
At
atmospheric pressure the highest CO2 adsorption capacities, measured in
millimolars per gram, for the best carbon spheres, were around 4.0 at 0 °C and
2.9 at 25 °C.
This new
approach brings several advantages over existing methods of producing carbon
spheres. It is alkali-free and it doesn’t need a catalyst to trigger the
shaping of the spheres. It uses a cheap and safe feedstock that is readily
available in the market. There is no need for solvents to purify the material.
It is also a rapid and safe procedure.
Dr. Saeid
Khodabakhshi of the Energy Safety Research Institute at Swansea University, who
led the research, said:
“Carbon
spheres are fast becoming vital products for a green and sustainable future.
Our research shows a green and sustainable way of making them.
We
demonstrated a safe, clean and rapid way of producing the spheres. Crucially,
the micropores in our spheres means they perform very well in capturing carbon.
Unlike other CVD methods, our procedure can produce spheres at large scale
without relying on hazardous gas and liquid feedstocks.
Carbon
spheres are also being examined for potential use in batteries and
supercapacitors. So in time, they could become essential to renewable energy
storage, just as they already are for carbon capture.â€
The
research was published in the journal Carbon.