Edge-carboxylated graphene nanoplatelets as efficient electrode materials for electrochemical supercapacitors

Deb Nath, Narayan Chandra,Jeon, In-Yup,Ju, Myung Jong,Ansari, Sajid Ali,Baek, Jong-Beom,Lee, Jae-Joon Elsevier 2019 Carbon Vol.142 No.-

<P><B>Abstract</B></P> <P>Edge-carboxylated graphene nanoplatelets (<B>ECG</B>), prepared by a mechano-chemical reaction (or ball milling method) in the presence of dry ice, are eligible for an efficient electrode materials for electrochemical supercapacitors. <B>ECG</B> contained a higher content of edge-carboxylic groups with less structural defects, compared with the nitrogen-doped carboxylic graphene (<B>NGOOH</B>) prepared from the conventional solution-exfoliation of graphite. The structural defects level of <B>ECG</B> is <I>ca</I>. 16.2%, while it was <I>ca</I>. 48.9% for <B>NGOOH</B>. The edge-carboxylation increases the electroactive surface area, hydrophilicity and wettability of graphene without serious deterioration of the intrinsic properties <I>e.g</I>., chemical, mechanical and electronic properties. In result, it is more effective in enabling ion adsorption and rapid electrolyte diffusion within the pores of graphene which results in a significant increase of specific capacitance (<I>C</I> <SUB>sp</SUB>) to 365.72 F/g at a current density of 1 A/g, with a good charge–discharge property and rate capability for <B>ECG.</B> On the other hand, the <I>C</I> <SUB>sp</SUB> significantly decreases to <I>ca.</I> 175.05 F/g for <B>NGOOH</B>, as its high level of structural defects seriously affected its electronic properties.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

On the displacement potential solution of plane problems of structural mechanics with mixed boundary conditions

Nath, S. K. Deb,Ahmed, S. Reaz,Kim, Sung-Gaun Springer-Verlag 2010 Archive of applied mechanics Vol.80 No.10

Stand-alone photoconversion of carbon dioxide on copper oxide wire arrays powered by tungsten trioxide/dye-sensitized solar cell dual absorbers

Deb Nath, Narayan Chandra,Choi, Seung Yo,Jeong, Hye Won,Lee, Jae-Joon,Park, Hyunwoong Elsevier 2016 Nano energy Vol.25 No.-

<P><B>Abstract</B></P> <P>A photoelectrochemical (PEC) cell composed of a WO<SUB>3</SUB>/dye-sensitized solar cell (WO<SUB>3</SUB>/DSSC) and copper oxide (Cu<SUB>x</SUB>O, where <I>x</I>=1 and 2) wire arrays as a dual-absorber photoanode and cathode, respectively, is demonstrated as a stand-alone, durable device for CO<SUB>2</SUB> photoconversion. The Cu<SUB>x</SUB>O wire arrays, which have high surface-to-volume ratios, exhibit promising electrocatalytic activity for CO<SUB>2</SUB> conversion to CO at Faradaic efficiencies of ~80% and ~60% at E=−0.2 and −0.4V <I>vs</I>. RHE, respectively, and H<SUB>2</SUB> production is minimized at a Faradaic efficiency <~20% in the potential range between −0.2 and −1.0V <I>vs</I>. RHE. The single-absorber cell of a WO<SUB>3</SUB> photoanode and Cu<SUB>x</SUB>O wire array cathode couple (WO<SUB>3</SUB>-Cu<SUB>x</SUB>O) requires a minimum overpotential of ~0.7V to drive CO<SUB>2</SUB> conversion. For stand-alone CO<SUB>2</SUB> conversion, a DSSC is coupled to the WO<SUB>3</SUB>-Cu<SUB>x</SUB>O system. In the dual-absorber cell (WO<SUB>3</SUB>/DSSC-Cu<SUB>x</SUB>O), the long-wave band (λ ><I>ca</I>. 450nm) passed through the semitransparent WO<SUB>3</SUB> film is absorbed by the dye-sensitized TiO<SUB>2</SUB> electrode of the DSSC. The WO<SUB>3</SUB>/DSSC-Cu<SUB>x</SUB>O shows a potential gain of ~0.7V and is able to successfully drive CO<SUB>2</SUB> conversion on Cu<SUB>x</SUB>O and simultaneously oxidize water on WO<SUB>3</SUB> without an external power supply. In this stand-alone system, the primary CO<SUB>2</SUB> conversion product is CO, with a solar-to-chemical energy efficiency of ~2.5%; H<SUB>2</SUB> and formate are obtained with energy efficiencies of 0.7% and 0.25%, respectively, in 5h (overall efficiency ~3.45%). Neither CO<SUB>2</SUB> conversion product nor H<SUB>2</SUB> is found using the single-absorber system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Stand-alone photoelectrochemical cell for CO<SUB>2</SUB> conversion was designed. </LI> <LI> WO<SUB>3</SUB>/DSSC and copper oxide (Cu<SUB>x</SUB>O) wire arrays were coupled as a dual-absorber photoanode and cathode, respectively. </LI> <LI> In the dual-absorber cell, the long-wave band passed through the semitransparent WO<SUB>3</SUB> film is absorbed by DSSC. </LI> <LI> The primary CO<SUB>2</SUB> conversion product is CO, with an energy efficiency of ~2.5% (overall efficiency ~3.45%). </LI> <LI> Neither CO<SUB>2</SUB> conversion product nor H<SUB>2</SUB> is produced by the single-absorber system. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Analytical solution of a stiffened orthotropic plate using alternative displacement potential approach

Nath, S K Deb,Ahmed, S Reaz,Kim, S-G SAGE Publications 2010 Proceedings of the Institution of Mechanical Engin Vol.224 No.1

Kinetic Features of the Cobalt Dihalide/Methylaluminoxane Catalytic System in 1,3-Butadiene Polymerization

Nath Dilip Chandra Deb,Fellows Christopher M.,Shiono Takeshi The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.3

The kinetic features of polymerization with an active site comprising cobalt dihalides ($CoX_2$, where X=Cl, Br, I) activated by methylaluminoxane (MAO) were investigated in 1,3-butadiene polymerization. The catalytic system exhibited the characteristic features of living polymerization. The initiation ($k_i$) and propagation ($k_p$) rate coefficients were estimated using the kinetic model for slow initiation previously reported by Shiono et al. The energy of activation fur the propagation reaction was calculated to be 27-30 $kJmol^{-1}$. The marked changes in reaction rate observed with different halides could be adequately described in terms of variations in the initiation process, with the same Arrhenius curve fitting propagation rate coeffcients estimated from all three halides, suggesting that the halide does not participate in the growing chain end.

BMP-2 Immoblized in BCP-Chitosan-Hyaluronic Acid Hybrid Scaffold for Bone Tissue Engineering

Nath, Subrata Deb,Abueva, Celine,Sarkar, Swapan Kumar,Lee, Byong Taek Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.12

In this study, we fabricated a novel micro porous hybrid scaffold of biphasic calcium phosphate (BCP) and a polylectrolyte complex (PEC) of chitosan (CS) and hyaluronic acid (HA). The fabrication process included loading of CS-HA PEC in a bare BCP scaffold followed by lypophilization. SEM observation and porosimetry revealed that the scaffold was full of micro and macro pores with total porosity of more than 60 % and pore size in the range of $20{\sim}200{\mu}m$. The composite scaffold was mechanically stronger than the bare BCP scaffold and was significantly stronger than the CS-HA PEC polymer scaffold. Bone morphogenetic growth factor (BMP-2) was immobilized in CS-HA PEC in order to integrate the osteoinductive potentiality required for osteogenesis. The BCP frame, prepared by sponge replica, worked as a physical barrier that prolonged the BMP-2 release significantly. The preliminary biocompatibility data show improved biological performance of the BMP-2 immobilized hybrid scaffold in the presence of rabbit bone marrow stem cells (rBMSC).

On the elastic, elastic-plastic properties of Au nanowires in the range of diameter 1-200 nm

Deb Nath, S. K.,Kim, Sung-Gaun American Institute of Physics 2012 JOURNAL OF APPLIED PHYSICS - Vol.112 No.12

Carbon Nanotubes on Fluorine-Doped Tin Oxide for Fabrication of Dye-Sensitized Solar Cells at Low Temperature Condition

Nath, Narayan Chandra Deb,Ahammad, A. J. Saleh,Sarker, Subrata,Rahman, Md. Mahbubur,Lim, Sung-Su,Choi, Won-Youl,Lee, Jae-Joon American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7

<P>The multi-walled carbon nanotubes (MWCNTs), electrophoretically deposited on fluorine-doped tin oxide (FTO), were employed as charge-collecting channels in the TiO2 photoelectrode of dye-sensitized solar cells (DSSCs) fabricated at 200 degrees C. The CNT-networks at the conducting substrate increased the charge collection efficiency of the porous TiO2 film, while the short circuit current increased up to ca. 43% under optimized condition. However, the significant decrease in the open-circuit voltage (Voc) up to ca. 132 mV resulted in the failure of the overall cell efficiency improvement. Findings reveal that the transfer process for the back electron is mainly responsible for the significant Voc drop when the MWCNTs were deposited at the electron-collecting substrate of the photoelectrode. The study demonstrates that electrophoretic deposition of MWCNTs on charge collecting substrate would be applicable to introduce an effective charge-collecting channel for the fabrication of flexible DSSCs under low temperature sintering condition.</P>

Ethylene-Polypropylene Copolymer as an Effective Sealing Spacer for Dye-Sensitized Solar Cells

Nath, Narayan Chandra Deb,Lee, Hwi Yong,Son, Younggon,Lee, Jae-Joon American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11

<P>Long-term stability is a major issue preventing the practical application of dye-sensitized solar cells (DSSCs). The DSSC stability problem relates to the sealing methods, which usually employ thermoplastic sealants. In the present study, a series of metallocene-catalyzed ethylene-polypropylene copolymers (EPCs) were prepared for application in DSSCs as sealing spacers. Different silane coupling agents and ethylene contents were investigated in the preparation of the EPCs to enhance the transparency, thermal-creep resistance, and strength of the adhesion to the glass substrate. The EPC films melted at similar to 80 degrees C and exhibited strong adhesion to glass after cooling, along with a high thermal-creep resistance. The films were transparent, insulating, water-resistant, and non-corrosive to the iodine-based electrolyte. The DSSCs sealed with optimized EPC films exhibited excellent stability during an aging time of 3 days, retaining similar to 98% of their initial efficiency, and were comparable to Surlyn. Therefore, the use of the EPC instead of the Surlyn polymer could drive substantial research interest for the commercialization of stable DSSCs with a low cost.</P>

Binary redox electrolytes used in dye-sensitized solar cells

Nath, Narayan Chandra Deb,Lee, Jae-Joon Elsevier 2019 Journal of industrial and engineering chemistry Vol.78 No.-

<P><B>Abstract</B></P> <P>Fast dye-regeneration and slow charge recombination are prerequisites for selecting superior redox couples of electrolytes to obtain highly efficient dye-sensitized solar cells (DSSCs). Although the ubiquitous combination of the I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> redox couple demonstrates high power conversion efficiency (PCE), it suffers from several limitations such as a large potential difference of approximately 560 mV between the Fermi level of I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> and the HOMO level of the N719 dye as well as high visible light absorption. These limitations cause inefficient dye-regeneration and significantly enhance the back reaction rate of photoelectrons to I<SUB>3</SUB> <SUP>−</SUP> in the electrolyte. This review discusses recent progress in the conception and device performance of different binary redox couples in DSSCs based on lowering potential differences, the back reaction of photo-induced electrons, the absorption of visible light, and improvement of dye-regeneration. We specifically focus on recent strategies targeted for effectively increasing both the open circuit voltage of DSSCs up to ˜100 mV and the PCE to above 10%; these strategies include introduction of binary redox couples or additional redox species to conventional iodine-based electrolytes. Moreover, we propose future directions for the further development of binary redox couples with advanced concepts for achieving DSSCs with high performance and high stability.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>