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Sher Shah, Md. Selim Arif,Park, A Reum,Zhang, Kan,Park, Jong Hyeok,Yoo, Pil J. American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.8
<P>A series of TiO<SUB>2</SUB>–reduced graphene oxide (RGO) nanocomposites were prepared by simple one-step hydrothermal reactions using the titania precursor, TiCl<SUB>4</SUB> and graphene oxide (GO) without reducing agents. Hydrolysis of TiCl<SUB>4</SUB> and mild reduction of GO were simultaneously carried out under hydrothermal conditions. While conventional approaches mostly utilize multistep chemical methods wherein strong reducing agents, such as hydrazine, hydroquinone, and sodium borohydride are employed, our method provides the notable advantages of a single step reaction without employing toxic solvents or reducing agents, thereby providing a novel green synthetic route to produce the nanocomposites of RGO and TiO<SUB>2</SUB>. The as-synthesized nanocomposites were characterized by several crystallographic, microscopic, and spectroscopic characterization methods, which enabled confrimation of the robustness of the suggested reaction scheme. Notably, X-ray diffraction and transmission electron micrograph proved that TiO<SUB>2</SUB> contained both anatase and rutile phases. In addition, the photocatalytic activities of the synthesized composites were measured for the degradation of rhodamine B dye. The catalyst also can degrade a colorless dye such as benzoic acid under visible light. The synthesized nanocomposites of biphasic TiO<SUB>2</SUB> with RGO showed enhanced catalytic activity compared to conventional TiO<SUB>2</SUB> photocatalyst, P25. The photocatalytic activity is strongly affected by the concentration of RGO in the nanocomposites, with the best photocatalytic activity observed for the composite of 2.0 wt % RGO. Since the synthesized biphasic TiO<SUB>2</SUB>–RGO nanocomposites have been shown to effectively reduce the electron–hole recombination rate, it is anticipated that they will be utilized as anode materials in lithium ion batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-8/am301287m/production/images/medium/am-2012-01287m_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am301287m'>ACS Electronic Supporting Info</A></P>
Arif Sher Shah, Md. Selim,Zhang, Kan,Park, A. Reum,Kim, Kwang Su,Park, Nam-Gyu,Park, Jong Hyeok,Yoo, Pil J. The Royal Society of Chemistry 2013 Nanoscale Vol.5 No.11
<P>With growing interest in the photocatalytic performance of TiO2-graphene composite systems, the ternary phase of TiO2, graphene, and Ag is expected to exhibit improved photocatalytic characteristics because of the improved recombination rate of photogenerated charge carriers and potential contribution of the generation of localized surface plasmon resonance at Ag sites on a surface of the TiO2-graphene binary matrix. In this work, Ag-TiO2-reduced graphene oxide ternary nanocomposites were successfully synthesized by a simple solvothermal process. In a single-step synthetic procedure, the reduction of AgNO3 and graphene oxide and the hydrolysis of titanium tetraisopropoxide were spontaneously performed in a mixed solvent system of ethylene glycol, N,N-dimethylformamide and a stoichiometric amount of water without resorting to the use of typical reducing agents. The nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, along with different microscopic and spectroscopic techniques, enabling us to confirm the successful reduction of AgNO3 and graphite oxide to metallic Ag and reduced graphene oxide, respectively. Due to the highly facilitated electron transport of well distributed Ag nanoparticles, the synthesized ternary nanocomposite showed enhanced photocatalytic activity for degradation of rhodamine B dye under visible light irradiation.</P>
Sher Shah, Md. Selim Arif,Lee, Jooyoung,Rauf, Ali,Park, Jong Hyeok,Lim, Byungkwon,Yoo, Pil J. The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.41
<P>Pt, a representative electrocatalyst for the oxygen reduction reaction (ORR), has suffered from high cost and poor stability, and thus it is essential to develop alternative electrocatalyst with a high catalytic activity comparable to Pt. Herein, we propose a rationally designed metal-free electrocatalyst with exposed active sites using an N, P, and S ternary-doped and graphene-incorporated porous carbon foam. We developed a novel template-free synthetic approach wherein the electrostatically-mediated complexation of graphene oxide (GO) with 2-aminothiazole (2AT) and branched polyethylenimine (PEI) in the presence of phytic acid (PA) was first induced, followed by a carbonization process to drive the formation of a three-dimensionally interconnected porous carbon foam. The resulting electrocatalyst exhibited a high pore volume and greatly extended specific surface area along with exposed active sites. Benefiting from these properties, the synthesized ternary-doped carbon foam displayed an outstanding electrocatalytic activity for the oxygen reduction ORR through four-electron transfer pathways. We observed that the remarkably improved ORR performance of the synthesized materials manifested an onset and a half-wave potential, mostly close to those of the commercially available ORR electrocatalyst of 20 wt% Pt/C while securing a greater stability in alkaline media.</P>
Sher Shah, Md. Selim Arif,Lee, Jooyoung,Park, A. Reum,Choi, Youngjin,Kim, Woo-Jae,Park, Juhyun,Chung, Chan-Hwa,Kim, Jaeyun,Lim, Byungkwon,Yoo, Pil J. Elsevier 2017 ELECTROCHIMICA ACTA Vol.224 No.-
<P><B>Abstract</B></P> <P>SnO<SUB>2</SUB> is a well-studied anode material for lithium ion batteries (LIBs). However, it undergoes severe capacity fading because of a large volume change (∼300%) during cycling. Composites of SnO<SUB>2</SUB> with electro-conductive graphene would deliver improved capacity and rate performance. Nevertheless, achieving the theoretical capacity of SnO<SUB>2</SUB> is still elusive, mainly because of disintegration of the active material from graphene and severe aggregation of SnO<SUB>2</SUB>, or Sn nanoparticles produced upon cycling. To surmount these limitations, in this work, nanocomposites containing ultra-fine sized SnO<SUB>2</SUB> nanoparticles (UFSN) with reduced graphene oxide and amorphous carbon were synthesized in a single step at low temperature and environmentally benign way, in which ascorbic acid was employed as the carbon source and reducing agent. UFSN could decrease the lithium ion diffusion path length. As a result of effective buffering effect afforded by the mesoporous structure against volume change and improved lithium ion diffusivity, the ternary nanocomposite achieves ultra-high capacity of 1245mAhg<SUP>−1</SUP> after 210 cycles at 100mAg<SUP>−1</SUP> and excellent cycling stability. Since the proposed approach is facile, straightforward, and highly reproducible, it is anticipated that this system would be a potential alternative to the conventional graphite anode for LIBs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Sher Shah, Md. Selim Arif,Kim, Woo-Jae,Park, Juhyun,Rhee, Do Kyung,Jang, In-Hyuk,Park, Nam-Gyu,Lee, Jun Young,Yoo, Pil J. American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.23
<P>Although silver bromide has recently drawn considerable attention because of its high photocatalytic activity, it tends to form agglomerated metallic silver under the irradiation of visible light. Therefore, photocatalytic activity decreases with time and cannot be applied for repeated uses. To overcome this limitation, in the present work, we complexed AgBr with nitrogen doped (N-doped) and amine functionalized reduced graphene oxide (GN). N-doped and/or amine functionalized graphene shows intrinsically good catalytic activity. Besides, amine groups can undergo complexation with silver ions to suppress its reduction to metallic Ag. As a result, these complexed catalysts show excellent photocatalytic activity for the degradation of methylene blue (MB) dye under the irradiation of visible light. Photocatalytic degradation of MB shows that the catalytic activity is optimized at a condition of 0.5 wt % GN, under which ∼99% of MB was degraded only after 50 min of visible light irradiation. Notably, the complexed catalyst is quite stable and retained almost all of its catalytic activity even after greater than 10 repeated cycles. Moreover, the catalyst can also efficiently decompose 2-chlorophenol, a colorless organic contaminant, under visible light exposure. Detailed experimental investigation reveals that hydroxyl (·OH) radicals play an important role for dye degradation reactions. A relevant mechanism for dye degradation has also been proposed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-23/am5051422/production/images/medium/am-2014-051422_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5051422'>ACS Electronic Supporting Info</A></P>
( Md. Selim Arif Sher Shah ),유필진 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
SnS2, a 2D layered transition metal dichalcogenide, is well studied as anode in lithium ion battery. However, it undergoes huge volume change during charging / discharging cycles. As a result its capacity fades with the increasing cycles. Composites of SnS2 with graphene deliver improved capacity and rate performance. Nevertheless, these composites rarely achieve theoretical (645 mAh/g) capacity of SnS2. In the present work, 3D macroporous nanostructures were achieved through the composite formation of SnS2 with reduced graphene oxide (RGO) and graphitic carbon nitride (g-C3N4). Several composites were synthesized by varying the amount of g-C3N4. Crystal phase, morphology and compositions of the composites were established through several characterization techniques and their lithium storage properties were evaluated. It showed that the specific capacity depends on the amount of N in the composites. High specific capacity and good rate performance were achieved in the ternary composite which otherwise was not possible in the binary composites. The ternary composites exhibit high specific capacity at high current densities like 1000 mA/g and 2000 mA/g. Moreover, ternary composites display good rate performance at different current densities and capacity retained when the current density comes back to the starting value.