Myunggoo Kang

Simultaneous reduction and nitrogen doping of graphite oxide by using electron beam irradiation

Nitrogen-doped graphenes (NGs) were successfully obtained by electron beam (e-beam) irradiation from graphite oxide (GO) colloid solution in the presence of aqueous ammonia at room temperature under ambient conditions. The morphology, structure, and components of the obtained NGs were characterized by scanning electron microscopy, Raman spectroscopy, powder X-ray diffraction, elemental analysis, and X-ray photoelectron spectroscopy. The amount of incorporated nitrogen was in the range ∼3.20–3.54 wt% with pyrrolic-N as the main nitrogen configuration. The results of this study show that nitrogen was simultaneously doped into graphene as the GO was reduced by e-beam irradiation. Herein, the ratio of nitrogen sites (pyridinic-N, pyrrolic-N, graphitic-N, and pyridinic-N-oxide) and specific surface area were controlled for various applications of the NGs as a function of irradiation dose. Increasing concentrations of graphitic-N and pyridinic-N-oxide enhanced the electrical conductivity and improved the kinetic performance of supercapacitor. The highest capacitance of 90.5 F g−1 at a charge/discharge current of 0.1 A g−1 in organic media was achieved for NG-300 because of a high BET specific surface area of 470 m2 g−1.

Charge transferred doping of single layer graphene by mono-dispersed manganese-oxide nanoparticles adsorption

We report an efficient and controllable method to introduce p-type doping in graphene by decoration with Mn3O4 nanoparticles (NPs) on mechanically exfoliated single layer graphene. A monolayer of Mn3O4 NPs, with a diameter in the range of 5–10 nm, was decorated on a graphene film using an ex-situ method, whereas by controlling the coverage of the NPs on the graphene surface, the carrier concentration could be continually adjusted. The p-type of the NP-decorated single layer graphene was confirmed by the Raman G-band. It was found that the carrier concentration could be gradually adjusted up to 26.09 × 1012 cm−2, with 90% coverage of Mn3O4 NPs. The Dirac point of the pristine graphene at the gate bias of 27 V shifted to 150 V for Mn3O4 NP decorated graphene. The p-type graphene doped with Mn3O4 NPs demonstrated significant high air-stability, even under an oxygen atmosphere for 60 days. This approach allows for the opportunity for simple, scalable, and highly stable doping of graphene for future high-perfo...

Pore Parameters-Dependent Adsorption Behavior of Volatile Organic Compounds on Graphene-Based Material

Mesoporous graphenes (MPGs) with interpenetrating porous networks are successfully obtained by the pyrolysis of composite gel consisting of graphite oxide (GO) and the amphiphilic triblock copolymer (Pluronic P123) under Ar atmosphere, wherein P123 is used as a soft-template. The as-prepared composite gel is obtained following self-assembly and freeze-drying. The obtained MPGs have high BET specific surface area (531-746 m2 g-1 and ink-bottle like pores with three dimensional interconnected network. Furthermore, the specific surface area and porous parameters such as pore volume, pore size, and pore size distribution of MPGs can be rationally controlled by regulating the initial mass ratio of P123 to GO. With the increase of P123 ratio, the average mesopore size is decreased from ∼16.4 nm to ∼9.5 nm, which is similar to the diameter size of P123 micelles. Also, the adsorption capacities of MPG-20 for 52 indoor air standard components (100 μg mL-1, Supelco) are compared with two different materials, namely commercial porous polymers (2,6-diphenyleneoxide) and reduced graphene oxide (RGO). The result shows that MPG-20 has significantly better adsorption capacity than RGO but also similar or slightly better than commercial porous polymer. The mesoporous structure and surface chemistry of MPGs were the most important factors for the enhancement of the adsorption efficiency for volatile organic compounds.