Production of two-dimensional layeredmaterials－graphite oxide and grapheneby plasma electrochemistry an¬d MoS2 nanosheets by quenching method

• Main Authors: Dang, Van Thanh, 鄧文成
• Other Authors: Wei,Kung-Hwa
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/cwpfbr

博士 === 國立交通大學 === 材料科學與工程學系所 === 102 === The purpose of this work is to find out new approaches for one-pot synthesis of graphite oxide and graphene by plasma electrochemical exfoliation of graphite in a basic electrolyte solution in a short-reaction time with regards of environmental friendliness, energy/time saving, and low cost. First of all, we adopted a highly efficient cathodic plasma (CP) process in which the vapor plasma envelope calorific effect provides instant oxidation and expansion of graphite for producing plasma-expanded graphite oxides (PEGOs) from recycled graphite electrodes (GEs) or high purity graphite (HG), within a reaction time of 10 min without the need for strong oxidants or concentrated acids. X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the dramatic structural change from GEs or HG to graphite oxides after the CP process. Furthermore, scanning electron microscopy and transmission electron microscopy revealed that the graphite oxide possessed a spheroidal morphology, with dimensions of 1–3 μm, as a result of melting and subsequent quenching during the plasma electrolysis process. We obtained a stable, homogeneous dispersion of PEGOs in N-methyl-2-pyrrolidone after sonication and filtering of the centrifuged PEGOs. We used these spheroidal graphite oxide particles as effective adsorbents for the removal of pollutants (e.g., Methylene Blue) from aqueous solutions. These PEGOs also served as good precursors for the preparation of graphite nanopletets. iv Sequently, we have demonstrated a new and highly efficient plasma-assisted electrochemical exfoliation method, involving a plasma-generated graphite cathode and a graphite anode, for the production of graphene sheets from electrodes in a basic electrolyte solution in a short reaction time. The AFM images revealed a lateral dimension of approximately 0.5–2.5 μm and a thickness of approximately 2.5 nm, corresponding to approximately seven layers of graphene, based on an interlayer spacing of 0.34 nm. Additively, the influence of electrolytic concentration on morphological and structural properties of plasmaelectrochemically exfoliated graphene is investigated and presented. Finally, we developed an efficient solution-based method for the production of few-layer MoS2 nanosheets through exfoliation of bulk MoS2 compounds that were subject to quenching in liquid N2 and subsequent ultrasonication. AFM images of individual nanosheets revealed that the thickness varied from 1.5 to 3.5 nm and the lateral dimensions from 0.5 to 3.5 μm.