The Synthesis And Application Of Of 3D Nitrogen-Doped Porous Carbon/Graphene

Supercapacitors and fuel cells as the energy store and transfer devices, with the excellent properties of ultra-long cycle-life, environmental-friendly, and so on, have received lots of attention. The electrode materials of supercapacitors and the catalysts of fuel cells are the critical factors for the development. While carbon materials have shown great potential as adsorbents, electrode materials, catalysts, and so on, which has already become the research focus recent years due to the significant performance of superior chemical stability, thermal conductivity, great adsorptivity, controllable pore structure, high specific surface area, high mechanical strength and the low cost of fabrication. In addition, graphene has become one of the best candidates for electrode materials due to the excellent characteristic of the high specific surface area(2630 m2/g), high electrical conductivity, structural stability, the low cost, and so on.In general, there is a low relatively specific capacitance(~200 F/g) for the carbon materials, also no active sites of oxygen reduction, which is difficult to meet the application in supercapacitors and fuel cells. Therefore, it is still the focus on improving the structure and performance of the carbon materials at home and abroad.Based on the above discussion, a novel route was used to synthesis the high performance three-dimensional(3D) nitrogen-doped porous carbon/graphene with different structure. This work discussed the effects of the different experimental conditions on the structure and electrochemical performance for the N-doped porous carbon materials. Furthermore, the effects of the different nitrogen doping types on the electrocatalytic performance of oxygen reduction for the carbon materials. The details are as follows:(1) The polypyrrole(PPy)/graphene oxide(GO) composite(PGO) was synthesized via in situ chemical polymerization. And then, PGO as the precursor was chemical activated using KOH as the activating agent to obtain the N-doped porous carbon/graphene(NPCG). The effects of the calcination temperature and the mass ratio(GO/Py) on the electrochemical performance of the as-prepared materials were discussed. The result showed that the high-performance 3D N-doped porous carbon material(NPCG15-650), as the mass ratio of GO to Py was 1:15 and the activated temperature was 650 ℃ by KOH, displayed good electrochemical performance: the specific surface area reached 1489 m2/g with 4.52% of the N-doped content. In addition, the specific capacitance of NPCG15-650 reached 398 F/g at 1 A/g and alsoshowed the good cycle stability(94%) after 1000 charge/discharge cycle.(2) The PPy/GO composite(GP) was synthesized using the nanosphere PPy and GO through the hydrothermal process. Then, the 3D N-doped porous carbon/graphene with larger specific surface area was prepared via the activation of KOH. The electrochemical performance of the as-prepared materials were discussed through the mass ratio of PPy to GO and the activated temperature. The morphology and structure of the samples were characterized by SEM, TEM, XPS, and so on. When Rm(GO:PPy)=1:12 with 650℃ of the activated temperature, the as-prepared sample(GPC12-650) displayed the large specific surface area(1807.6 m2/g) and the hierarchical pore structure proofed by the pore size distribution curve and SEM. The specific capacitance of GPC12-650 was as high as 521 F/g at the current density of 1A/g, and retaining 372 F/g at 20 A/g. Furthermore, GPC12-650 exhibited the high capacitance retention(94.3%) after 1000 charge-discharge cycles at the high current density of 10 A/g.(3) The phenylenediamine(OPD, MPD, and PPD) was added in to the precursor(GP) to control the structure and the types of nitrogen doping for the carbon/graphene to obtain the 3D N-doped network architecture. The result found that the 3D N-doped network porous carbon/graphene material(GPPC) was prepared successfully as the mass ratio(Rm(GO:PPy:phenylenediamine)=1:12:3) and the activated temperature(650 ℃) by KOH. GPPC not only presented the excellent 3D porous structure, also showed the cross-linked network framework with the large specific surface area(2597.8 m2/g). The specific capacitance of GPPC could reach 567.3 F/g at 1 A/g with the high capacitance retention of 94.6% at 10 A/g. Moreover, GPPC exhibited the good catalytic of oxygen reduction with the oxygen reduction peak centered at-0.18 V and the start potential at-0.105 V. It also could be found that not only the content of N-doped can make the effect on the catalytic activity of the carbon materials, also can enhance the catalytic of oxygen reduction of the as-prepared samples when the content of N-5 and N-6 were dominant in the types of N-doped.