Sundara Ramaprabhu

Cost-effective counter electrode (CE) with high electrocatalytic performance is very much essential for the wide application of dye-sensitized solar cells (DSSC). The 1D-2D carbon heterostructure (Pt/GR@CNT) with low platinum (Pt) loading has been synthesized by a facile in situ microwave-assisted polyol-reduction method. The excellent electrocatalytic activity as well as photovoltaic performance was achieved due to the combination of 2D graphene nanoribbons (GR) and 1D multi-walled carbon nanotubes (CNT) with high catalytically active Pt nanoparticles. Microwave-assisted longitudinal unzipping of few outer layers of CNTs along with co-reduction of Pt nanoparticles is an effective method to create electrochemically active defective edge sites, which have a crucial role in enhancing electrochemical performance. Synergistic effect of ultra-fine Pt nanoparticles, partially unzipped graphene nanoribbons and inner core tubes of CNTs modulates the power conversion efficiency of solar cell to 5.57% ± 0.03 as compared with 4.73% ± 0.13 of CNTs. Pt/GR@CNT CE even with low Pt loading of 14 μg cm−2 showcases equivalent performance with that of pure Pt counter electrode. [Figure not available: see fulltext.]

In the present wok, we have demonstrated the simultaneous removal of sodium and arsenic (pentavalent and trivalent) from aqueous solution using functionalized graphite nanoplatelets (f-GNP) based electrodes. In addition, these electrodes based water filter was used for multiple metals removal from sea water. Graphite nanoplatelets (GNP) were prepared by acid intercalation and thermal exfoliation. Functionalization of GNP was done by further acid treatment. Material was characterized by different characterization techniques. Performance of supercapacitor based water filter was analyzed for the removal of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water, using cyclic voltametry (CV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic (both trivalent and pentavalent). Maximum adsorption capacities of 27, 29 and 32 mg/g for arsenate, arsenite and sodium were achieved in addition to good removal efficiency for sodium, magnesium, calcium and potassium from sea water. © 2010 Elsevier B.V.

Despite possessing 5-fold higher specific energy density compared to commercial lithium-ion batteries, the insulating nature of sulfur and its reductive derivatives along with the uncontrollable migration of polysulfides hinder the commercialization of lithium-sulfur technology. Herein a bilayer cathode consisting of nitrogen sulfur codoped porous carbon network and titanium carbide has been introduced and investigated methodically. The porous sulfur host promotes uninterrupted diffusion of electrolyte and ions whereas titanium carbide acts as polysulfide trapping material. The superiority of this bilayer cathode over the conventional interlayer approach has been highlighted in terms of the diffusivity of lithium ions and the overall ohmic resistance. Variation in interfacial charge transfer resistance during charging and discharging has been investigated using dynamic electrochemical impedance spectroscopy. Discharge capacity reaches as high as 1300 mA h g-1 at 0.1 C with a Coulombic efficiency of 99%. Theoretical studies reveal that the polar nature and improved interfacial charge transfer between the TiC and polysulfides result in excellent binding strength and faster redox kinetics during operation, respectively. This work provides an experimental as well as theoretical evidence of the bifunctional mechanism of TiC toward polysulfide confinement and conversion.

Materials play a key role especially in the field of energy storage and conversion. Design of efficient and cost-effective materials for energy applications is of prime research focus. This chapter presents the recent trends in the energy-related applications of various carbon nanotubes (CNT) and their hybrid nanostructures. Development of CNT-based electrocatalysts for proton exchange membrane fuel cells and CNT-based electrodes for supercapacitors and Li-ion batteries are discussed.

Herein, we report, the fabrication of a mechanically stable, flexible graphene based all-solid-state supercapacitor with ionic liquid incorporated polyacrylonitrile (PAN/[BMIM][TFSI]) electrolyte for electric vehicles (EVs). The PAN/[BMIM][TFSI] electrolyte shows high ionic conductivity (2.42 mS/cm at 28 °C) with high thermal stability. Solid-like layered phase of ionic liquid is observed on the surface of pores of PAN membrane along with liquid phase which made it possible to hold 400 wt% of mobile phase. This phase formation is facilitated by the ionic interaction of C. N moieties with the electrolyte ions. A supercapacitor device, comprised PAN/[BMIM][TFSI] electrolyte and graphene as electrode, is fabricated and the performance is demonstrated. Several parameters of the device, like, energy storage and discharge capacity, internal power dissipation, operating temperature, safe operation and mechanical stability, meet the requirements of future EVs. In addition, a good cyclic stability is observed even after 1000 cycles. © 2012 Elsevier Ltd.

Herein, we report the synthesis of mesoporous titanate and titania nanoparticles and their application in Dye sensitized solar cells (DSSCs). The samples were adequately characterized. DSSCs fabricated with titanate and titania particles had a maximum efficiency of ∼0.8% and 2.1%, respectively. The variation in solar cell parameters with increasing thickness was also investigated and the results have been discussed. © 2011 American Institute of Physics.

Eu3+ doped YVO4 nano phosphors were synthesized by adopting a simple Co-Precipitation Method (CPM). In order to compare and evaluate this method's potentiality, we prepared the same phosphor by using a conventional Solid State Reaction method (SSR). X-Ray Diffraction (XRD) profile confirms the tetragonal nature of Eu3+ doped YVO4 nano phosphors. The efficiency of the prepared phosphors was analyzed by means of its emission spectral profiles. We also observed a rich red emission from the prepared phosphors under a Ultra-Violet (UV) source. Such luminescent powders are expected to be applied as red phosphors in display device applications. In addition, Scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier-Transform IR spectroscopy (FTIR), and Raman Spectrum were also used to characterize the synthesized phosphor. © 2011 The Korean Institute of Metals and Materials and Springer Netherlands.

Novel foam composites comprising functionalized graphene (f-G) and polyvinylidene fluoride (PVDF) were prepared and electrical conductivity and electromagnetic interference (EMI) shielding efficiency of the composites with different mass fractions of f-G have been investigated. The electrical conductivity increases with the increase in concentration of f-G in insulating PVDF matrix. A dramatic change in the conductivity is observed from 10 -16 S · m-1 for insulating PVDF to 10-4 S · m-1 for 0.5 wt.% f-G reinforced PVDF composite, which can be attributed to high-aspect-ratio and highly conducting nature of f-G nanofiller, which forms a conductive network in the polymer. An EMI shielding effectiveness of ≈20 dB is obtained in X-band (8-12 GHz) region and 18 dB in broadband (1-8 GHz) region for 5 wt.% of f-G in foam composite. The application of conductive graphene foam composites as lightweight EMI shielding materials for X-band and broadband shielding has been demonstrated and the mechanism of EMI shielding in f-G/PVDF foam composites has been discussed. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water pollution is a major problem in the global context and main cause of some diseases especially in India. Graphene has fascinated the scientific community by its different novel properties for various applications. In the present work, we have synthesized the graphene sheets by hydrogen induced exfoliation of graphitic oxide followed by functionalization. Graphene sheets were characterized by electron microscopy, X-ray diffraction, infra-red and Raman spectroscopy techniques. These functionalized graphene sheets were used for simultaneous removal of high concentration of inorganic species of arsenic (both trivalent and pentavalent) and sodium from aqueous solution using supercapacitor based water filter. In addition, these functionalized graphene sheets based water filter was used for desalination of sea water. Adsorption isotherms and kinetics were studied for the simultaneous removal of sodium and arsenic. Maximum adsorption capacities, using Langmuir isotherm, for arsenate, arsenite and sodium were found to be nearly 142, 139 and 122. mg/g, respectively. High adsorption capacity for both inorganic species of arsenic and sodium along with desalination ability of graphene based supercapacitor provides a solution for commercially feasible water filter. © 2011 Elsevier B.V.

Carbon nanomaterials are promissing electrode materials for supercapacitor applications due to their unique properties. Electrolyte accessibility is a big challenge in ionic liquid electrolyte-based supercapacitors with carbon nanomaterials as electrodes. In this study, an ultrahigh performance supercapacitor electrode, based on solidlike ionic liquid layer coated carbon nanotubes-hydrogen exfoliated graphene nanocomposite is demonstrated with hydrophobic ionic liquid as electrolyte. The presence of solidlike layers of ionic liquid is confirmed by structural and morphological analysis. The nanocomposite shows extremely high energy density (171 Wh/kg) and high specific capacitance (201 F/g) at a large specific current of 2 A/g, in terms of the mass of active electrode material, along with wide operating voltage (3.5 V). The Ragone fit shows that the time constant, maximum stored energy, and maximum available power are 0.575 s, 170.66 Wh/kg, and 148.43 kW/kg, respectively. The improvement in performance of the nanocomposite is mainly attributed to the presence of solidlike layers of ionic liquid on the surface of carbon nanomaterials, which effectively increases the electrolyte accessibility and number of shortest, directional ion transport paths. Here, carbon nanotubes play a role as a smart conductive spacer. © 2012 American Chemical Society.