Synthesis of high carbon content microspheres using 2-step microwave carbonization, and the influence of nitrogen doping on catalytic activity

Abstract

In the present work, nitrogen-containing carbon particles were synthesized by a two-step microwave carbonization. Nitrogen was introduced into the carbon particles via the addition of urea solution during microwave-assisted hydrothermal carbonization. The nitrogen content was easily controlled by varying the urea concentration. Carbon microspheres of over 90% carbon content by atomic ratio were obtained using the microwave-assisted hydrothermal carbonization of glucose solutions, followed by the secondary microwave treatment of the dried samples. The effects of further microwave irradiation on the oxygen reduction reaction catalytic activity of nitrogen containing carbon particles were studied. This study showed that microwave-assisted hydrothermal carbonization, followed by additional microwave treatment can produce oxygen reduction reaction catalytic active carbon materials which contain nitrogen as catalytic active sites in conducting hexagonal layers of carbon structures. It is meaningful that carbon materials are obtained from environmental friendly starting materials biomass derivatives, under mild reaction condition.