Swansea team develops faster, greener way of producing carbon spheres

A fast, green and one-step method for producing porous carbon spheres—a 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. Microscopy image a) shows agglomerated spheres while single spheres can be seen from images b-d). Credit: ESRI, Swansea University

The method produces spheres that have good capacity for carbon capture, and it works effectively at a large scale. The research was published in the journal  Carbon .

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.

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.

The work of the Swansea team points the way towards a better, cleaner and greener way of producing carbon spheres.

The team adapted chemical vapor deposition (CVD), which 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 which is readily available in the market. There is no need for solvents to purify the material.

• It is a rapid and safe procedure.

Resources

• Saeed Khodabakhshi, Sajad Kiani, Yubiao Niu, Alvin Orbaek White, Wafa Suwaileh, Richard E. Palmer, Andrew R. Barron, Enrico Andreoli (2021) “Facile and environmentally friendly synthesis of ultramicroporous carbon spheres: A significant improvement in CVD method,”  Carbon , Volume 171, Pages 426-436, doi: 10.1016/j.carbon.2020.08.056

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Taxonomy

• Absorbents
• Heavy metals