Study On The Preparation And The Application Of Graphene Based Two-dimensional Porous Materials

Graphene, the 2D lattices of sp2 carbon atoms, has spurred great research interest as electrode materials in LIBs owing to the following features:First, the high intrinsic surface area and outstanding electrical conductivity of graphene provide an ideal platform for the storage and transportation of lithium ions and electrons. Second, graphene derivates with different oxygen containing groups such as graphene oxide (GO) and reduced graphene oxide (RGO) can serve as appealing 2D substrates for the anisotropic growth of various metal or metal oxide nanoparticles as electrode mateials. The aggregation of these NPs during the cycling can be effectively suppressed by the graphene matrices. Recently, graphene and graphene-based composites has spurred great research interest as electrode materials. Since porous materials generally possess permanent porosity, low mass densities, synthetic diversification, and high physicochemical stability, which make them highly competitive in gas storage and separation applications. A carbonaceous material with the single layer consisting of carbon atoms, was found, graphene and graphene-based novel composites. In this paper, The details are exhibited as follows:(1) Cyclopentadienyliron (CpFe) groups have been successfully attached on the surfaces of reduced graphene oxide (rG) by a ligand-exchange reaction of ferrocene (Cp2Fe) and rG, to produce CpFe-modified reduced graphene oxide (rGFeCp), which exhibits good processability in many organic solvents. In a similar one-pot performance, the graphite was efficiently exfoliated using Cp2Fe as the intercalators, to form CpFe-attached free-standing graphene nanosheets (GfeCp,-10 layers). Upon pyrolysis and ammonia activation, rGFeCp and GfeCp were converted to iron/nitrogen co-doped porous graphenes, rGFe-800a and Gfe-800a, respectively. The obtained rGFe-800a exhibited good electrochemical performance for oxygen reduction reaction (ORR) under alkaline condition (0.1 M KOH), with a low half-wave potential of -0.29 V, a dominant four-electron transfer mechanism (n=3.5 at -1.0 V), a maximum diffusion-limiting current density of 4.86 mAcm-2 and excellent methanol tolerance. The exhibited ORR catalytic performance, stability as well as methanol tolerance for rGFe-800a are superior to commercial 20% Pt/C, demonstrating its promising application as ORR catalyst for fuel cells and metal-air batteries. The nitrogen configuration and Fe species of rGFe-800a was investigated thoroughly and believed to correlate with the high catalytic activity.(2) Three graphene-directed conjugated two-dimensional porous polymers (GMP-1, GMP-2 and GMP-3) have been synthesized by the sonogashira coupling. Their chemical structures were confirmed by Fourier transform infrared spectroscopy (FT-IR) and solid-state I3C CP/MAS measurements. And the thermal stability of these materials was tested by thermogravimetric analysis (TGA) under nitrogen. The crystallinity of GMP series were carried out by X-ray diffraction (XRD). The morphology and microstructure of the materials were investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (TEM). The N2 sorption isotherms were measured at 77K to characterize the porosity of the network. The apparent surface areas of GMP-1, GMP-2 and GMP-3 are 920 m2g-1,636 m2g-1, and 211 m2g-1 respectively which are comparative when compared to other reported networks. The pore size distribution indicated that the materials have an arrow pore size distribution between 1.3 and 4.0 nm. More importantly, the porous polymers exhibit outstanding CO2 and H2 uptake. More importantly, the porous polymers exhibit outstanding CO2 and H2 uptake. The most CO2 uptake is up to 95.2 mg g-1 (GMP-1) in 273K and 1 bar, which are among the highest reported for porous materials. And the most H2 uptake is up to 113 mg g-1 (GMP-1) in 77K and 1 bar. The Qst values for GMP-1, GMP-2, and GMP-3 are 35, 25 and 21 kJ mol-1, respectively. The values are higher than those of other porous materials. The polymer networks exhibit good ideal selectivities for CO2/N2. The results above show that GMP series might be classified as promising materials for CO2 storage and separation applications.