The present work introduces a new method for the recycling of waste flocculation sludge to prepare electrode materials for supercapacitor. Hazardous azo dye was removal from textile dying wastewater by a new chitosan-based flocculant, and the generated dye sludge flocs was used as a nitrogen-containing precursor for the fabrication of N-doped carbon materials. The influence of azo dye on specific surface areas, nitrogen content, pore evolution of the resulting products and their electrochemical performance were investigated in detail. The results demonstrated a dual role of azo dye worked as both a nitrogen resource and pore-forming agent. The resulting N-doped carbon nanosheets derived from azo dye flocs demonstrated high electrochemical capacitance and good stability for supercapacitor electrode, which is attributed to the unique nitrogen doping, higher specific surface area and efficient charge transfer ability.

High-quality and solution processable graphene sheets are produced by a simple electrochemical exfoliation method and employed as a high-power anode for lithium-ion batteries (LIBs). The electrochemically exfoliated graphene (EEG) composed of a few layers of graphene sheets, have low oxygen content and high C/O ratio (~ 14.9). The LIBs with EEG anode exhibit ultrafast lithium storage and excellent cycling stability, but low initial efficiency. The excellent rate capability and cycling stability are attributed to the favorable structural and chemical properties of the EEG, but the large irreversibility needs to be overcome for practical applications.

Two dimensional(2D) crystals, composed of a single layer or a few atomic layers extracted from layered materials are attracting researchers’ interest due to promising applications in the nanoelectromechanical systems. Worldwide researchers are preparing devices with suspended 2D materials to study their physical and electrical properties. However, during the fabrication process of 2D flakes on a target substrate, contamination occurs, which makes the measurement data less reliable. We propose a dry transfer method using poly-methyl methacrylate(PMMA) for the 2D flakes to transfer onto the targeted substrate. The PMMA is then removed from the device by an N-Methyl-2-pyrrolidone solution and a critical point dryer, which makes the suspended 2D flakes residue free. Our method provides a clean, reliable and controllable way of fabricating micrometer-sized suspended 2D nanosheets.

In this study, graphene oxide(GO) was used as drug carriers to amorphize poorly watersoluble drugs via a co-spray drying process. Two poorly water-soluble drugs, fenofibrate and ibuprofen, were investigated. It was found that the drug molecules could be in the graphene nanosheets in amorphous or nano crystalline forms and thus have a significantly enhanced dissolution rate compared with the counterpart crystalline form. In addition, the dissolution of the amorphous drug enwrapped with the graphene oxide was higher than that of the amorphous drug in activated carbon (AC) even though the AC possessed a larger specific surface area than that of the graphene oxide. The amorphous formulations also remained stable under accelerated storage conditions (40°C and 75% relative humidity) for a study period of 14 months. Therefore, graphene oxide could be a potential drug carrier and amorphization agent for poorly water-soluble drugs to enhance their bioavailability.

Until now, single MFI nanosheets have been prepared using a multi-step approach based on the exfoliation of layered MFI, followed by centrifugation to remove nonexfoliated particles. This top-down method is time-consuming, costly and low-yield and it produces fragmented nanosheets with sub micrometre lateral dimensions. Alternatively, direct (bottom-up) synthesis could produce high-aspect-ratio zeolite nanosheets, with improved yield and at lower cost. Here we use a nanocrystal-seeded growth method triggered by a single rotational intergrowth to synthesize high-aspect-ratio MFI nanosheets with a thickness of 5 nanometres (2.5 unit cells). These high-aspect-ratio nanosheets allow the fabrication of thin and defect-free coatings that effectively cover porous substrates. These coatings can be intergrown to produce high-flux and ultra-selective MFI membranes that compare favourably with other MFI membranes prepared from existing MFI materials (such as exfoliated nanosheets or nanocrystals).

Nitrogen-doped carbon nanosheets with a developed porous structure were prepared from polyurethane foams by hydrothermal carbonization following ZnCl2 chemical activation. Scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, solid state 13C nuclear magnetic resonance (NMR) spectra and X-ray photoelectron spectroscopy were used to characterize the nitrogen-doped carbon nanosheet structure and composition. The removal of Cr(VI) by the N-doped carbon nanosheets was investigated. The results showed that the maximum removal capacity for chromium of 188 mg/g was found at pH=2.0 with PHC-Z-3. pH had an important effect on Cr(VI) removal and the optimal pH was 2.0. Moreover, amino groups and carboxyl groups in the nitrogen-doped carbon nanosheet played important roles in Cr(VI) removal, and promoted the reduction of Cr(VI) to Cr(III).

그래핀 기반 소재는 높은 가공성과 초박성으로 인하여 분리막 소재로서 각광받고 있다. 본 연구에서는, 스핀 코팅 법을 이용하여 제조된 산화그래핀 분리막의 기체 투과 거동을 평가하였다. 산화그래핀 분리막의 구조는 산화그래핀의 크기와 산화그래핀 용액의 pH 조절을 통하여 조절될 수 있다. 산화그래핀의 크기가 작을수록 굴곡률이 작아짐에 따라 분리막의 기 체 투과도 및 선택도가 증가하는 경향을 보인다. 또한 산화그래핀에서의 기체 투과 거동은 적층된 산화그래핀 사이의 채널 크기에 따라 영향을 받는다. 특히 산화그래핀 분리막의 좁은 기공과 이산화탄소 선택적인 산화그래핀 자체의 특성으로 인하 여 산화그래핀 분리막은 이산화탄소에 대한 높은 투과도 및 선택성을 가지며, 이는 이산화탄소 포집에 적합한 특성을 가진다. 이러한 산화그래핀 분리막의 특이한 기체 투과 거동은 흡착-촉진 확산 거동(표면 확산 기작)으로 설명될 수 있다. 본 연구를 통하여 이산화탄소 선택성 분리막 소재 설계와 슬릿 형태의 기공과 적층 구조를 가진 분리막을 통한 기체 투과 거동 연구가 활발히 이루어질 것으로 기대한다.

The development of nanostructured functional materials derived from biomass and/or waste is of growing importance for creating sustainable energy-storage systems. In this study, nanoporous carbonaceous materials containing numerous heteroatoms were fabricated from waste coffee grounds using a top-down process via simple heating with KOH. The nanoporous carbon nanosheets exhibited notable material properties such as high specific surface area (1960.1 m2 g–1), numerous redox-active heteroatoms (16.1 at% oxygen, 2.7 at% nitrogen, and 1.6 at% sulfur), and high aspect ratios (>100). These unique properties led to good electrochemical performance as supercapacitor electrodes. A specific capacitance of ~438.5 F g–1 was achieved at a scan rate of 2 mV s–1, and a capacitance of 176 F g–1 was maintained at a fast scan rate of 100 mV s–1. Furthermore, cyclic stability was achieved for over 2000 cycles.

Nitrogen-atom doped graphene oxide was considered to prevent the dissolution of polysulfide and to guarantee the enhanced redox reaction of sulfur for good cycle performance of lithium sulfur cells. In this study, we used urea as a nitrogen source due to its low cost and easy preparation. To find the optimum urea content, we tested three different ratios of urea to graphene oxide. The morphology of the composites was examined by field emission scanning electron microscope. Functional groups and bonding characterization were measured by X-ray photoelectron spectroscopy. Electrochemical properties were characterized by cyclic voltammetry in an organic electrolyte solution. Compared with thermally reduced graphene/sulfur (S) composite, nitrogen-doped graphene/S composites showed higher electroactivity and more stable capacity retention.

Due to their morphology, electrochemical stability, and function as a conducting carbon matrix, graphene nanosheets (GNS) have been studied for their potential roles in improving the performance of sulfur cathodes. In this study, a GNS/sulfur (GNS/S) composite was prepared using the infiltration method with organic solvent. The structure, morphology and crystallinity of the composites were examined using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The electrochemical properties were also characterized using cyclic voltammetry (CV). The CV data revealed that the GNS/S composites exhibited enhanced specific-current density and ~10% higher capacity, in comparison with the S-containing, activated-carbon samples. The composite electrode also showed better cycling performance for multiple charge/discharge cycles. The improvement in the capacity and cycling stability of the GNS/S composite electrode is probably related to the fact that the graphene in the composite improves conductivity and that the graphene is well dispersed in the composites.

Nanocomposites comprised of graphene oxide (GO) nanosheets and magnesium oxide (MgO) nanoparticles were synthesized by a sol-gel process. The synthesized samples were studied by X-ray powder diffraction, atomic force microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. The results show that the MgO nanoparticles, with an average diameter of 70 nm, are decorated uniformly on the surface of the GOs. By controlling the concentration of the MgO precursors and reaction cycles, it was possible to control the loading density and the size of the resulting MgO particles. Because the MgO particles are robustly anchored on the GO structure, the MgO/GOs nanocomposites will have future applications in the fields of adsorption and chemical sensing.