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Reduction of Graphite Oxide by Using an Atmospheric Pressure Plasma
Niyitanga THEOPHILE,Hae Kyung JEONG 한국물리학회 2016 New Physics: Sae Mulli Vol.66 No.5
We present a simple, fast, eco-friendly, low-cost method to reduce graphite oxide (GO) by using an atmospheric pressure plasma. The ambient plasma is directly applied to a GO solution for a short time. Changes in the morphology, the compositions of carbon and oxygen, the electrochemical properties, and the impedance are investigated for GO before and after the plasma treatment. After the plasma treatment, amount of oxygen is reduced from 30 to 26 at% and the impedance is reduced by about 23%. In addition, after the treatment, the specific capacitance is increased from 13 to 19 F/g, indicating better electrochemical performance for supercapacitor applications. Therefore, an ambient plasma applied directly to a GO solution should be a simple and easy approach for effective reduction of GO and is good for use in various industries.
Activated-Carbon-Supported Molybdenum Disulfide for the Enhanced Hydrogen Evolution Reaction
Niyitanga THEOPHILE,정혜경 한국물리학회 2020 New Physics: Sae Mulli Vol.70 No.5
Molybdenum disulfide, a two-dimensional graphene-like material, is an alternative candidate catalyst to the expensive platinum due to its lower cost and abandance on earth. However, the conductivity of molybdenum disulfide needs to be improved to have excellent electrocatalytic behaviors. Herein, we report an efficient molybdenum disulfide supported by activated carbon for the hydrogen evolution reaction through the hydrothermal method. The as-prepared activated carbonmolybdenum disulfide (AC-MoS2) composite presents a small overpotential ( 0:16 V), which is very much smaller in comparison to that for the precursor MoS2 without AC ( 0:31 V) at the same current density of 10 mAcm 2. The composite also exhibited high stability at 5000 cycles and excellent durability after 24 hours. The AC-MoS2 composite demonstrated its smallest resistance (23 Ω) at high frequency (3000 kHz) in comparison with the precursor (9038 Ω), proving that the conductivity of the as-prepared composite is increased. The good performance of AC-MoS2 is assigned to the synergic effect of AC and MoS2 which has a positive effect on enhancing the catalytic activity for the hydrogen evolution reaction.
Niyitanga, Theophile,Jeong, Hae Kyung Elsevier 2019 International journal of hydrogen energy Vol.44 No.2
<P><B>Abstract</B></P> <P>We report an efficient molybdenum disulfide (MoS<SUB>2</SUB>) supported by thermally reduced graphite oxide and carbon nanotubes (TRGO-CNT) for hydrogen evolution reaction. The TRGO-CNT-MoS<SUB>2</SUB> composite is successfully prepared by a simple sonication process, exhibiting excellent catalytic activity of the hydrogen evolution reaction (HER) with a low overpotential of −0.14 V, which is much lower compared to that of MoS<SUB>2</SUB>, CNT-MoS<SUB>2</SUB> and TRGO-MoS<SUB>2</SUB>, respectively. TRGO-CNT-MoS<SUB>2</SUB> also exhibits high stability even after 1000 cycles and strong durability after 48 h. The high HER performance of TRGO-CNT-MoS<SUB>2</SUB> attributes to a synergic effect of thermal reduced GO and CNT that support MoS<SUB>2</SUB> due to significant decrease of electrochemical impedance and reliable supporting material for the efficient HER.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The TRGO-CNT-MoS<SUB>2</SUB> composite was prepared by a simple sonication method. </LI> <LI> Lower overpotential of −0.14 V was obtained. </LI> <LI> CNT, a bridge-like in the composite, enhanced the conductivity of TRGO-MoS<SUB>2</SUB>. </LI> <LI> The composite exhibited strong stability and long durability. </LI> </UL> </P>
Rosaiah Pitcheri,Divya Ponnusamy,Sambasivam Sangaraju,Tighezza Ammar M.,Kalaivani V.,Muthukrishnaraj A.,Ayyar Manikandan,Niyitanga Theophile,Kim Haekyoung 한국탄소학회 2024 Carbon Letters Vol.34 No.1
Synthesis of extremely competent materials is of great interest in addressing the energy storage concerns. Manganese oxide nanowires (MnO2 NWs) are prepared in situ with multiwall carbon nanotubes (MWCNT) and graphene oxide (GO) using a simple and effective hydrothermal method. Powder XRD, Raman and XPS analysis are utilized to examine the structural characteristics and chemical state of composites. The initial specific discharge capacity of pure MnO2 NWs, MnO2 NWs/MWCNT and MnO2 NWs/rGO composites are 1225, 1589 and 1685 mAh/g, respectively. The MnO2 NWs/MWCNT and MnO2 NWs/rGO composites showed stable behavior with a specific capacity of 957 and 1108 mAh/g, respectively, after 60 cycles. Moreover, MnO2 NWs/rGO composite sustained a specific capacity of 784 mAh/g, even after 250 cycles at a current density of 1 A/g showing outstanding cycling stability.