Swansea University researchers have reported that they have developed ‘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.
According to the researchers, this 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 emits it into the atmosphere.
According to the researchers, 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 require a chemical to activate them.
The Swansea team, based in the University’s Energy Safety Research Institute, adapted an existing method known as CVD – chemical vapour 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.
Findings of the research included:
- 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.
According to the research team, this approach brings ‘several advantages’ over existing methods of producing carbon spheres, as it is alkali-free and doesn’t need a catalyst to trigger the shaping of the spheres, uses ‘a cheap and safe feedstock’ which is readily available in the market and doesn’t need solvents to purify the material.
Dr Saeid Khodabakhshi of the Energy Safety Research Institute at Swansea University, who led the research, commented on the findings: “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.”
The research, Facile and environmentally friendly synthesis of ultramicroporous carbon spheres: A significant improvement in CVD method, has been published in the Carbon journal.
This research was first reported by the University of Swansea website.
