Researchers have developed simple methods to synthesize carbon nanomaterials such as carbon nanotubes and graphene-like nanosheets from low-grade coal. These could potentially be used in making electronic devices and as catalyst for breaking down harmful chemicals under sunlight1, 2.
Coal is one of the major sources of carbon. Existing techniques such as arc discharge, catalytic hydrocarbon decomposition and hot-filament chemical vapour deposition are used to make carbon nanomaterials from coal. These methods require high temperature and multi-step chemical treatment.
In search of alternative methods, scientists from CSIR-North East Institute of Science and Technology, Assam treated low-quality coal with sodium hydroxide, potassium hydroxide and hydrochloric acid and heated the mixture at 350 degree Celsius
Such treatment reduced ash yield and removed soluble silica and alumina from the coal. The alkali penetrated the coal structure, forming irregular micropores and nanopores. Sophisticated imaging techniques revealed the formation of carbon nanoparticles such as carbon nanotubes and nanoballs.
When the coal was treated with nitric acid, sodium hydroxide and hydrochloric acid, it formed onion-like fullerene and graphene-like nanosheets which were able to break down harmful organic pollutants such as nitrophenol under sunlight.
“These coal-derived carbon nanomaterials could also be used for electrode materials such as capacitor for energy-storing devices to deal with the current situation of energy deficiency,” says lead scientist Binoy K. Saikia from the CSIR-NEIST.