Highly Porous Carbon Nanospheres and Carbon Foams for Supercapacitors Using Facile Spray Pyrolysisand One-Pot Reaction

Due to their unique properties, high surface area carbon nanomaterials such as carbon nanotubes and

graphene have been widely used in energy storage applications. However, it is still difficult and

expensive to synthesize carbon nanotubes and graphene at large-scales. Hence, there is still a need for

the development of low-cost and facile synthesis techniques for porous carbon materials with highly

accessible surface areas.

A facile and solution-based, spray pyrolysis synthesis technique which was used to synthesize individual

carbon nanospheres with specific surface area (SSA) up to 1106 m2/g using a novel ZnO catalyzed

reaction. The carbon nanosphere diameters were tunable from 10 nm to several micrometers by varying

the precursor concentrations. Solid, hollow, and porous carbon nanospheres were achieved by simply

varying the ratio of catalyst and carbon source without using any templates. When evaluated as

supercapacitor electrode materials, specific capacitances of up to 112 F/g at a current density of 0.1 A/g,

were observed, with no capacitance loss after 20,000 cycles. The performance of the carbon

nanospheres as electrodes in Li-ion batteries were also investigated.

The direct pyrolysis of sugar and zinc nitrate mixtures was employed to obtain foam-like carbons with

specific surface area (SSA) up to 2340 m2/g without using any hard templates. The role of the ZnO

nanoparticles formed from the decomposition of zinc nitrate and the effects of high temperature

annealing on the formation of the high SSA carbon foams were systematically studied. Due to the facile

and quick reaction conditions, these carbon foams carbons could be easily synthesized at a large scale.

When used as supercapacitor electrode materials, a specific capacitance up to 280 F/g was achieved at

current density of 0.1 A/g, and still remained as high as 207 F/g even at a high current density of 10 A/g.

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C. Wang, Y. Wang, J. Graser, R. Zhao, F. Gao, M.J. O’Connell, ACS Nano, 7, 11156-11165 (2013).

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C. Wang, M.J. O’Connell, C.K. Chan, ACS Appl. Mater. Interfaces, 7, 8952 (2015).